pg. 1 

CONTENTS 4.4.1 Brief description of data reception station 1. RISAT-1 Satellite Overview

4.5 Detailed functional reception of data reception station

2. Mission Overview 2.1 Mission

Specifications 4.6 Antenna and tracking pedestal

2.2 Mission elements 4.6.1 Antenna 3. RISAT Specifications 4.6.2 Pedestal

3.1 RISAT-1 Orbit 4.6.3 Drive chain 4.6.4 Azimuth housing 3.2 RISAT Subsystems with

heritage / new element 4.6.5 Elevation housing 3.3 Mechanical Systems

4.7 Technical specifications 3.3.1 Structure

3.3.2 Coordinate System & Panel Nomenclature

4.8 Dual Polarized S/X band feed & RF systems 3.3.3 Mechanisms 4.8.1 Dual Polarized

S/X band Feed 3.4 Thermal 3.5 BDH 4.8.2 Feed

Specifications 3.6 SSR 3.7 RF Systems 4.8.3 X-band DPC

(Divider, Phase, Shifter, Coupler)

3.7.1 TTC RF 3.7.2 X-Band RF 3.8 SPS 4.8.4 S-band DPC 3.9 Power Systems 4.8.5 X-band Up/Down

Converter 3.10 On Board Computer (OBC) 4.8.6 X-band down

Converter 3.11 AOCS 3.12 Actuators 4.8.7 X-band Up

Converter 4. Data Reception Systems 4.1 Introduction 4.8.8 S-band Down

Converter 4.2 Station requirements to track and receive RISAT-1 data

4.8.9 Integrated tracking system

4.3 IMGEOS configuration 4.9 IF and Base band Systems 4.4 Data reception station

specifications

pg. 2 

8.4 Radiometric check 4.9.1 Programmable IF matrix 8.5 Band to band

registration (BBR) 4.9.2 IF Fiber optic link 9 Data Access and

Distribution 4.9.3 High data rate

demodulators 9.1 Services 4.10 Digital servo control

system 9.1.1 Polygon based query / ordering/ collects

4.11 Antenna drive unit 4.11.1 Antenna

control unit 9.1.2 Map sheet number based query

4.12 tracking network configuration

9.1.3 Location name based query

4.12.1 Station automation system 9.1.4 Point (Lat-Long )

based query 4.13 Station Control computer 9.1.5 Search for

images based on shape file

5 Level ‘ 0 Systems 5.1 Introduction

9.1.6 Search for images based on date of pass/ ordering

5.2 Station work flow manager

5.3 Data ingest system 5.4 Timing systems

9.2 Product status monitoring

5.4.1 IRIG-G time code translator

6 SAR payload for RISAT 9.3 Services for offline users 6.1 Modes of operation

10 Payload Programming 7 RISAT data products and formats 10.1 Introduction

10.1.1 Registered users

7.1 Raw signal products (Level-0)

10.1.2 Offline users

7.2 Ellipsoid Geocoded Products (Level-2)

10.1.3 Ground station users

7.3 Value added products 7.4 Image Quality

parameters 10.2 Payload Programming activity 8 Product quality control 10.2.1 Options for

placing the 8.1 Meta file verification 8.2 Format validation 8.3 Geometric check

pg. 3 

programming request

10.2.2 Request

status 10.2.3 PPS-

System 11 Applications 11.1 Forestry

11.2 Crop 11.3 Agricultural 11.4 Flood

1. RISAT-1 SATELLITE OVERVIEW

RISAT mission is envisaged to fly a SAR

imaging payload for supplementing to

the needs of remote sensing data

users across the globe. With its

pg. 4 

capabilities to operate in day, night and

all weather conditions, SAR is an

important sensor, which either in stand-

alone mode or as complementary to

electro-optical sensors, will cater to

diverse resources and environmental

monitoring applications even during

cloud cover times. The basic nature of

data, which is a function of a microwave

returned signal, will significantly

enhance the scope of satellite remote

sensing and develop newer applications.

RISAT will be launched by ISRO’s own

PSLV launch vehicle, as the launch

parameters are well within the

capabilities. The interface of the satellite

with the launch vehicle is through

circular merman band clamp (937VB

Version) to match with PSLV launcher

interface.

ii) To develop and operate a compatible

satellite to meet the mission

requirements operating in three axis

stabilized mode in 536.38 km circular

sun synchronous orbit.

iii) To establish ground segment to

receive and process SAR data.

iv) To develop related algorithms and

data products to serve in well

established application areas and also to

enhance the mission utility.

2.2Mission elements

To meet the defined mission objectives,

various components as required by the

mission including SAR payload, satellite,

orbit, satellite management in orbit and

data handling on ground have been

defined.

SAR mission will be operational in

nature. Mission specifications are

similar to contemporary international

missions. SAR payload has a multi-mode

capability for catering to

2. Mission

2.1Mission Objectives

The objectives of RISAT are, i)To

develop a multimode, agile SAR payload

operating in scanSAR, strip and spot

modes to provide images with coarse,

fine and high spatial resolutions

respectively.

• Continuous fine resolution strip mode

for initial reconnaissance, infrastructure

development applications, disaster

management etc. ,

pg. 5 

A polar sun synchronous orbit at 536.38

kms altitude and inclination of 97.554

deg. with repetivity cycle of 377 orbits in

25 days with a descending node local

time of 6:00 AM +/- 5 min is chosen .

Main guiding parameter for choosing the

orbit for RISAT-1 is achieving a global

coverage in a systematic way for a

given swath. Other considerations such

as interferometric applications, the

presence of atomic oxygen and

atmospheric drag have also been kept in

view. Orbit parameters are planned to

be variable as per mission operation

requirements for various imaging

modes.

• Wide swath scanSAR mode for agriculture, forestry, flood mapping, geological applications etc.

• High resolution spotlight mode for

special applications The satellite is fabricated to have agility

for maximizing the imaging in high-

resolution mode, with Data

transmission in real time as well as in

storage mode. RISAT technology has

been chosen so that the continuity is

maintained in follow-on missions of

RISAT.

Mission Elements of RISAT-1 are

presented in Figure :1 , and these will

result in theDevelopment of user-

friendly data products and data archival. 3.2RISAT Subsystems with

heritage /new elements Fig.1 Mission Elements of RISAT-1

3RISAT Specifications

3.1RISAT-1 Orbit:

RISAT-1 has 13 new sub systems, and

hertitage and past experience exists for

remaining 10 subsystems. Power Sub

systems works on 70 V bus, generated

from CFRP based solar panels and 70

AH Ni-H battery. Miniaturized version of

TTC-RF sub systems and High data rate

modulator, Phase locked loop based

Xband system are used. Phase array

antenna is used for SAR data

transmission using Dual polarized wave

pg. 6 

guide radiating elements. SPS sub

system is same as used in Carto-2

mission. INSAT type SPSS, two axes

DSS, IRS-P6 Star sensor with

improvement in update rate, package

density and satellite interface to MIL-

STD-1553B interface, Conventional

conical earth sensor are used. 50NMS &

0.3NM Torque wheels , IRU sub systems

as in Carto-2 and (8+1) 11 N Thrusters

are used as actuators. SAR payload is

based on TR module based architecture.

BDH and SSR are new type of sub

systems for RISAT-1.

3.3 Mechanical systems

Radar Imaging satellite (RISAT) is built

around a bus for ongoing IRS missions

in the weight class of 2000kg. RISAT

weight is 1850 kg out of which SAR

payload weight is around 950 kg.

3.3.1 Structure

The main structure of RISAT consists of

one single cylinder of 2.77 m height

(approx). The bottom side of the

cylinder has a truncated triangular

structure to hold the SAR antenna and

major bus service elements. At the

topside of the cylinder a cuboid

structure to accommodate the solar

arrays, majority of the sensors and

antennae is provided. The triangular

structure with SAR antenna is identified

as PAYLOAD module and the cuboid

structure with solar arrays is called as

SOLAR PANEL module. Sufficientgap is

available between the payload module

and the solar panel module so that

there is no interference between the

solar array and the SAR antenna in

launch configuration as well as on-orbit

configuration.

3.3.2 Coordinate System & Panel

Nomenclature

The center of gravity of the satellite is

taken as the origin of the co-ordinate

system considered for the satellite

attitude control and attitude

determination purposes. Refer the

following figure for axis definition of

RISAT mission.

pg. 7 

Fig. 2 Roll, Yaw and Pitch Positive Yaw Axis From CG towards and

perpendicular to SAR antenna in

deployed configuration (towards center

of earth) Positive Pitch Axis From CG

towards the bottom deck of the

triangular structure supporting the SAR

Antenna. Positive Roll Axis Perpendicular

to +ve Yaw and +ve Pitch axis

completing the right handed system.

Roll axis is along the deployed SAR

Antenna.

3.3.3 Mechanisms

RISAT employs SAR deployment

mechanism andSolar array deployment

mechanism

3.4 Thermal

Thermal control will be provided using

space proven thermal control elements

such as OSR, MLI, paints, thermal

control tapes, quartz wool blanket, Sink

plates and heat pipes. Heaters will be

provided to maintain temperatures

during cold conditions. The orbit and

orientation of RISAT gives rise to the

following factors that decide the thermal

design approach of the Main Bus as well

as payload :No eclipse during winter and

equinox, Eclipse only during summer

(22 minutes maximum), Sun rays

incident on SAR radiator with small

incident angle resulting in high

temperature, More earthshine load on

Earth viewing panel due to reduced

altitude. Reduced albedo load due to

6AM/6PM equatorial crossing time

3.5 BDH The data handling system of RISAT is

configured in the form of two formatters

for each of RX1 (V) and RX2 (H)

receivers from the SAR payload. The

SAR data is transferred to BDH through

LVDS Serializer -Deserializer interface

where each data line is at the rate of

218.75 Mbps and clock signal of 31.25

MHz. The de-serialized output (SAR

Data) is written in memory as long as

the data window from SAR P/L is HIGH.

In the next data window, the SAR data

pg. 8 

is read from the memory by the

formatter for formatting along with

necessary auxiliary data. Two memories

per receiver are used for the ping-pong

operation of memory write and memory

read simultaneously. The formatter

clock is 32 MHz or 10 MHz depending

upon the data rates of SAR P/L. All

clocks are derived from 160 MHz crystal

oscillators. Null flag concept is used for

optimum utilization of SSR. When the

data rate of SAR P/L and BDH overhead

together is greater than 640Mbps, real

time transmission is not possible and

data have to be recorded in SSR.

Recorded data can be played back later.

Differential Encoder is used to remove

four-phase ambiguity of QPSK. BDH has

functionalities like payload interface,

formatter, 1553 interface, differential

encoding clock generation, final parallel

to serial conversion and DC/DC.

Main Mode Description

a) Standby mode

b) Retention mode

c) Record mode

d) Playback mode

3.7 RF Systems

3.7.1TTC RF

The TT&C (RF) system for RISAT

consists of two chains of PLL coherent

SBand Transponder connected to a

common antenna system (Two

antennae system consisting of main and

null filling antenna). The basic

configuration is identical to the ones

employed in earlier IRS missions. The

TC demodulation scheme is PSK/PCM

with a date rate of 4KBPS.

Frequencies:

Receiver frequency : 2071.875 MHz

Transmitter frequency : 2250.00 MHz

3.7.2 X-Band RF

The X-Band RF is required to do the

following operations: 3.6 SSR

The RISAT SSR has a capacity of 300 G

bits , realized with six memory boards of

50 G bits capacity each . The memory

boards, by default are configured into

two partitions each of 150 G bits with

three memory boards per partition.

To accept the payload data from the

base band Data Handling system.

To modulate the above data on two X-

Band carriers and transmit the

same to ground after suitable

amplification and filtering.

pg. 9 

In the proposed data transmission for

RISAT, half the data i.e. 320 MBPS will

be transmitted in right hand circular

polarisation (RHCP) and the remaining

320 MBPS in the left hand circular

polarisation (LHCP); two identical chains

operating at 8.2125 GHz are used to

transmit 640 MBPS of payload data. The

carrier generation section, QPSK

modulator section, filter units, selection

of Main and redundant chain units are

identical in all the chains as the

frequency of operation and modulation

schemes are identical. Both the chains

have end to end redundancy. The

spherical phased array antenna has

radiating elements distributed almost

uniformly on a hemispherical surface. It

generates a beam in the required

direction by switching ‘ON’ only those

elements, which can contribute

significantly towards the beam direction.

It is proposed to use the 64 element

array.

computing the state vector of the high-

dynamic platform.

3.9 Power Systems

Radar Imaging Satellite (RISAT) Power

System consists of Solar array with 6

panels of rigid Al honeycomb

sandwiched between CFRP face skin and

arranged in two wings with three panels

in each wing in +ve roll and -ve roll

axes, chemical Battery for power

storage and power electronics for power

conditioning and distribution. The power

system for RISAT is designed to (a)

meet the 6AM/6PM orbit illumination

conditions; (b) to cater to large power

requirement of HRSAR (High Resolution

Synthetic Aperture Radar) payload; and

(c) solar eclipse conditions during

summer solstice. The power system

configuration is arrived to meet all the

requirements and consists of a fully

regulated 70V Bus, regulated by Solar

array regulator during sunlit. Battery

Discharge Regulator (BDR) supports

power to the bus when the load demand

exceeds the array generation during

payload operation and eclipse conditions

by regulating the bus to 70V and

protected against over voltage, under

voltage, over current and is single point

3.8 SPS

Satellite Positioning System (SPS) for

RISAT comprises of 10-channel C/A

code GPS receiver at L1 (1575.42 MHz)

frequency. SPS is designed for

pg. 10 

failure proof. To provide the required

voltage to the subsystems which cannot

adopt to 70V bus within RISAT time

frame, there is a provision for auxiliary

bus of 42V which is fully protected and

distributed through two hubs as ABUS1

and ABUS2 each with separate high

current fuses. Further distribution to

individual users is from fuse boxes

placed at convenient locations. To

power the core power and uplink even

under Battery Emergency conditions

during eclipse two uninterrupted Buses

are formed by Or-ing Battery and Main

Bus. U-Bus1 and U-Bus2 will power Main

&Redt Domestic & OBC DC/DCs and are

distributed through separate fuses.

SADA is incorporated to compensation

for the reduction in power during space

craft +-36 deg rotations and eclipses.

The energy storage system for RISAT

employs a single NiH2 battery of 70AH

capacity, consisting of 42 cells. The

protection mechanism exists for battery

during over discharge conditions similar

to other spacecrafts. Power Electronics

elements ensure, regulation of solar

array power to regulate the bus,

performs battery managements and

distributes power to the various users.

Power Electronics subsystem also

consists of Domestic Regulator,

individual cell monitoring, Four-cell

logic, Battery charge controller, OBC

and GC Interfaces.

3.10 On Board Computer(OBC)

In order to minimize power, weight, and

volume, the spacecraft functions like

command, housekeeping (Telemetry),

Attitude and Orbit Control, Thermal

Management, Sensor data processing

etc., have been integrated into a single

package called On board computer

(OBC) which also implements the MIL

STD 1553B protocol for interfacing with

other subsystems of the spacecraft..

The use of MIL-STD-1553B interfaces

between OBC and other subsystems

greatly decreases the volume and mass

of

cabling and the associated connectors.

The OBC system is realizing the

following spacecraft functions:

• Sensor electronics

• Command Processing

• Telemetry and House-keeping

• Attitude and Orbit Control (AOCS)

Besides, the OBC interfaces with Power,

TM-TTC (RF) for command and

telemetry, Sensors, Heaters, Thrusters

pg. 11 

4 Actuators and Reaction Wheels through special

logics. A functionally redundant OBC is

also present. Either of the OBCs can be

selected for operation. It also

implements the 1553 protocol for

interfacing with other subsystems of the

spacecraft for

5 Eight Numbers of Canted 11 N

thrusters (Mono propellant drazine

system operating in blow down

mode) with two axis canting from

+Pitch axis for Acquisition and OM

operation. One Center 11 N

thruster for OM operation, four

Nos of Reaction Wheels of

Capacity (0.3 Nm Torque and 50.0

NMS @ 4410 RPM) mounted in

tetrahedral configuration about –

Pitch axis. Maximum Operating

Speed is upto ±4500 RPM.

Reaction wheels are used for

Normal Mode and for OM Rotation.

- 2 Magnetic Torquers of 60.0 A-

m2 Capacity mounted along Roll

and Pitch axis for Momentum

Dumping.

data transfer - Star Sensor, SPS, WDE,

DTG, DH, SSR and PAA.

11 AOCS

RISAT AOCS modules are derived from

Carto-2B with modifications

required for RISAT mission and are

implemented in OBC.

AOCS Specifications during Imaging are

stated as follows :

Pointing : ± 0.05 ° (3σ)

Drift Rate : ± 3.0 e-04 °/s (3σ)

The attitude orbit control system for

RISAT is configured with thefollowing

sensors:

4π Sun sensor

2 Nos. Magnetometer

2 Nos. IRU (Inertial Reference Unit)

Digital sun sensor 1 No., Solar panel

sun sensor 2 sets (4 Nos.)

3 Nos., RW 4 nos.and SADA, Star

Sensor 2 Nos., Earth sensor 2 Nos.,

pg. 12 

Basic system configuration of a high resolution Synthetic Aperture Radar (SAR) on an IRS

Mission Requirements

1.1 Mission Requirements Basic system configuration of a high resolution Synthetic Aperture Radar (SAR) on an IRS platform is outlined in this chapter. Primarily, the SAR system configuration is designed to meet the following basic objectives: ♦ It should meet applications

conforming to national requirements. ♦ It should be multimode one to meet

different resolution and swath requirements.

♦ It should be agile for minimizing revisit time and maximizing operational flexibility.

♦ Technology used should be state of the art, survive obsolescence and adaptable for other different frequency bands in future missions.

As the first development of spaceborne SAR in ISRO, the SAR will be developed for single frequency because of technical complexity and the need for developing the sensor in shortest possible time frame. From application considerations, the SAR will be designed in C-band with single/dual/quad polarization capability. For this purpose, active antenna technology with the capability of electronic beam steering, meeting all the above requirements of multi mode operation, agility and state of the art features, has been identified. Implementation of High Resolution SAR development is planned in two stages: ♦ Development of prototype model

SAR with scaled version of active antenna using commercial components. The basic aim is to

develop and demonstrate expertise at reduced cost.

♦ Subsequent delivery of flight model spaceborne SAR within a further time frame of 2 years.

1.2 Frequency and Polarization Selection

The selection of operational frequency and polarization are driven by the applications demanding a wide range of resolution / swath / polarization combinations. From resolution considerations, resolution cell should be sufficiently large in comparison with the wavelength (about 10 times the wavelength). Hence, typically 3 m is the highest resolution in L-band, 1.5 to 2 m in S-band, 1 m in C/X-bands and 10-20 cm in Ku/Ka band. Higher resolutions (1m or better) are feasible for C-band frequencies and higher because of bandwidth allocation considerations. Total bandwidth allocation for radar applications is 80 MHz for L-band, 210 MHz for C-band, 350 MHz for X-band and 500 MHz for X-band. Hence, for ground mapping and coastal applications, like oil slick & ships detection, etc. C- and X-band are preferred. For civilian applications like agriculture, soil moisture, forestry, flood mapping and ocean related studies both C- and L-band with cross polarization are preferred. Ocean related studies are served best by VV-polarization and land related

pg. 13 

studies are aided by HH-polarization. Provision of both co- and cross- polar data aids significantly in discrimination of features. Co-polar return is mainly affected by surface or canopy scattering. Cross-polar return is mainly governed by volume scattering which depends on penetration through canopy/surface. So, higher the frequency poorer will be the return in cross-polarization. Hence, polarimetry is best suited in lower frequency bands like P, L and C. Polarimetry is not usually applicable for X and higher frequency bands. These considerations have led to the choice of C-band frequency operation with single/dual/quad polarization capability to exploit the maximum gamut of applications.

1.3 Modes of Operation The RISAT High Resolution SAR will be operating in C-band at a frequency of 5.35 GHz. The spacecraft altitude has been fixed at 608.958 km from the 13-day repetivity considerations. The SAR system has been designed to provide constant swath for all elevation pointing and almost near constant minimum radar cross section performance. The proposed SAR will operate in the following basic modes, the details of which are given in Table-2.1. (Operational philosophy of the modes is briefly outlined here for better comprehensibility of the discussion that follows. Key issues pertaining to these modes are discussed later in this chapter under separate section.) • Fine Resolution Stripmap Mode-1

(FRS-1) with 3 m resolution. This mode is based on Stripmap imaging,

which is the conventional mode of SAR. In this, the orientation of the antenna beam is fixed with respect to flight path so that a strip of constant swath (here, 30 km) is illuminated along the flight direction. The stripmap SAR image dimension is limited only in the across track and not in the along track dimension (limited only by on-board recorder capacity).

• Coarse Resolution ScanSAR Mode (CRS) with 240 km swath. The ScanSAR mode allows for a multifold increase of the range swath dimension. This is achieved by periodically stepping the antenna beam to the neighboring subswaths (in the range direction). In this case, the radar is continuously ON, but only a portion of the full synthetic antenna length is available for each target in a subswath. This causes a degradation of the achievable azimuth resolution with respect to the strip map case. In other words, the range swath dimension increases at the expense of azimuth resolution. In the CRS-mode of RISAT, there will 12 beams to cover each sub-swath of 20 km (either side of the intermediate sub-swaths will have an overlap of 10 km from the preceding and succeeding sub-swaths, thereby reducing the effective sub-swath width from 30 km to 20 km). Therefore, total swath in CRS mode would be 240 km.

• Medium Resolution ScanSAR Mode (MRS) with 120 km swath. This is a 6-beam scanSAR mode, similar to the CRS mode.

• Fine Resolution Stripmap Mode-2 (FRS-2) with quad polarization

pg. 14 

capability. Philosophically, this mode is a hybrid stripmap&scanSAR. It is stripmap in the sense that the beam orientation is kept fixed with respect to the flight path and a strip of constant swath width is covered. Also, in a way it is similar to scanSAR, because for part of the aperture time the beam polarisation is switched from V-transmit to H-transmit, and vice-versa. Hence, this mode would be used for polarimetry, as we can have all the four combinations of polarisation, viz, VV, VH, HH& HV.

• High Resolution Spotlight Mode (HRS) with 1 m resolution. In the spotlight mode, the antenna beam is oriented continuously to illuminate a particular spot on the ground. This way, the target aperture time is increased which results in improved azimuth resolution (compared to that in the stripmap case). The improved resolution is obtained at the cost of azimuth coverage. The latter is partly improved by making use of sliding spotlight mode (hybrid spotlight-stripmap mode). This imaging would be done over a spot size of 10 km x 10 km. An experimental mode to extend the azimuth coverage upto 100 km is also planned in this.

These modes have been illustrated in Fig.2.1.

1.4 RISAT Imaging Geometry In order to provide greater flexibility in the selection of the look angles for different applications and to increase the effective repeatability, a region on the ground may be accessed by different look angles ranging from 9° to

47° corresponding to off-nadir distances of 100 km and 700 km, respectively. Hence, a repeatability period of 13 days may be reduced to 2 days. This look angle variation is effected by electronic switching of the antenna beam in the elevation direction. This electronic switching of the beams is also necessary for ScanSAR modes of operation (MRS/ CRS). As shown in Fig.-2.1, SAR will operate with basic elevation beam width of 2.48o -1.67o, over a total ground distance of 600 km, starting from an off nadir distance of 100 km and upto 700km. Radiometric performance is guaranteed for the swaths covered from off-nadir distance of 200 km to 600 km (qualified region) and for the regions lying between 100 km to 200 km and 600 km to 700 km, the performance is not guaranteed (unqualified). Figure –2.1 shows the basic system geometry of the proposed SAR for operation of all the above-mentioned modes. The variation of the look angle and incidence angle for various off-nadir distances is illustrated in Fig 2.2.

pg. 15 

200km 400km

608.958 km

200

490

2.480-1.670

EL.BEAM

100

700km

100km 540

100 km (UNQUALIFIED)

400 km (QUALIFIED)

200 KM

608.958 km

100 km (UNQUALIFIED)

FRS-1/FRS-2 Mode

MRS Mode

CRS Mode

HRS Mode

Fig.-2.1 Basic System Geometry and Operating Modes of High Resolution SAR

pg. 16 

Table-2.1

Major Mission Parameters for Spaceborne High Resolution SAR

Altitude 608.958Km Orbit Sun synchronous (6 AM / 6 PM equatorial crossing) Frequency 5.35 GHz Polarisation Single / Dual / Quad-polarization Swath coverage Either side of the flight track

Selectable within 100 – 700 km off-nadir distance (100-200 km & 600-700 km regions are unqualified,

the rest is qualified) Qualified (200-600 km)

18° - 43° Look angle coverage

Total 9° – 47° (100-700 km) Qualified (200-600 km)

20° – 49° Incidence angle coverage

Total 10° – 54° (100-700 km)

Antenna Microstrip Active antenna, 6m x 2m Peak Gain 44.5dB Total no. of beams 63 on each side of the flight track (total 126) On board storage SSR with 240 Gbits No. of TR Modules 288 Transmitted power per TRM

10 W

Antenna peak power 2.88 kW AverageDC Input Power 3.86 kW Range Compression On Ground Pulse width 20 μs Imaging Modes HRS FRS-1 FRS-2 MRS CRS Applicable Polarization combinations

Single & Dual

Single & Dual

Quad Single & Dual

Single & Dual

Swath/Spot (km)

Defined 10 (Az) x 10(Rng)

30 30 120 240

pg. 17 

Imaging Modes HRS FRS-1 FRS-2 MRS CRS Experimental

100 (Az) x

--- --- --- ---

10(Rng) Resolution 1m x

0.7m 3m x 2m

9m x 4m

21-23m x 8m

41-55m x 8m (Az x slant range)

Minimum sigma naught (dB)

-16.3 -17 -18 -18 -18

(Qualified Region) Chirp bandwidth (MHz) 225 75 37.5 18.75 18.75 Sampling frequency (MHz) 250 83.3 41.67 20.83 20.83

96-163 55-181 55-181 55-181 55-181 Data window (μs) PRF 3500± 3000± 3000± 3000± 3000±

200 Hz 200 Hz 200 Hz 200 Hz 200 Hz Qualified (200-600)Km

27040-37120

7424-14366

3840-7168

2048-3584

2048-3584

No. of Complex Samples

Total 23960-40720

4864-15104

2560-7680

1280-3840

1280-3840 (100-

700)Km Data Compression 3-bit BAQ Onboard BAQ (6/5/4/3/2 bits)

Considering 3-BAQ (for

100km azimuth)

6-BAQ 6-BAQ 6-BAQ 6-BAQ Data Rate (in Mbps)

Single pol 507-739 176-556 ---- 44-142 44-142 Dual pol 1014-

1478 352-1112

---- 88-284 88-284

Quad pol ---- ---- 176-556 ---- ---- Considering 3-BAQ

(for 100km

azimuth)

6-BAQ 6-BAQ 6-BAQ 6-BAQ Data Coverage/ Storage

Single pol 4 spots 2950 km

---- 11500 km

11500 km

Dual pol 2 spots 1475 km

---- 5750 km

5750 km

Quad pol ---- ---- 2950 km

---- ----

Azimuth Ambiguity -21 dB -22 dB (over qualified region) Range Ambiguity -20 dB -20 dB (over qualified region) Radiometric Resolution 3 dB (single look)

pg. 18 

Imaging Modes HRS FRS-1 FRS-2 MRS CRS Accuracy (over orbit)

2 dB (Goal) Performance (over qualified region)

Accuracy TBD (over Lifetime)

pg. 19 

In the non-imaging mode antenna will be looking downwards towards the nadir. By having an option of roll-tilting the satellite by ±34°, SAR can be made to see either side of the track (one at a time), thereby improving the revisit time by a factor of two. The pointing is chosen such that between two successive beam positions, swath overlap of 10 km is always ensured. This overlap is important for achieving MRS/CRS mode. Fast electronic beam pointing and beamwidth control is achieved by electronic elevation beam control in the active antenna. 61 beam-pointing positions have been identified to enable sufficient agility in imaging anywhere over 600 km region (qualified and unqualified) with best possible performance. Each beam is centered at off-nadir intervals of 10 km. Two additional beams with no pointing (0° w.r.t. antenna orientation angle i.e.

±34°) are defined for two halves of

antenna, 6m x 1m each. Therefore, there are 63 beam positions defined for imaging on each of the sides of the sub-satellite track. As a result, a total of 126 beams would be used for imaging on either sides of the track.

1.5 Antenna configuration –in brief and Elevation beamwidth considerations

Area of the SAR antenna is dictated by the frequency band of operation, and is of the order of 12 m2 for C-band operation. Hence, RISAT active antenna is configured with 6m (azimuth) x 2m (elevation/range) dimensions, with 288 pairs (V & H) of TR-modules. The RISAT antenna consists of three panels each of 2m×2m size, as shown in Fig.2.3, to facilitate stowing during launch and later, deployment in the space. The longer dimension of the antenna is aligned with azimuth direction and the width in the elevation/range direction. Each panel consists of 4 tiles of size 1m×1m, each consisting of 24×24 radiating elements. In the azimuth direction (antenna length) 24 elements are grouped together to be fed by a single TR-module pair (V/H polarization), hence we have 6 TR-module pairs in the antenna length direction. Each radiating element in the width direction is fed by a different TR-module pair, hence there are 48 (=24 x 2m) TR-module pairs in the antenna width. The total number of TR-module pairs is therefore 288 (=6m x 48). The inter-element spacing has been kept 0.7λ, where λ stands for wavelength which is 5.6 cm. If the spacing between the radiators is more than this, grating

Fig. 2.2 Variation of Angles with Off Nadir

pg. 20 

lobes will occur in the antenna patterns. At the junction of two tiles, the inter-element spacing is 1.4λ, therefore, one blank row of radiating elements may be assumed which is at a distance of 0.7λ from the nearest radiating elements from the adjacent tiles. In short, 49 rows of TR-modules may be assumed in the antenna width (for system analysis purposes), with the centre row as a hypothetical blank (inactive) one to attribute to the inter-tile spacing. Elevation beamwidth will be made to vary with pointing angles in order to

achieve pointing-independent swath of 30 km and constant minimum radar cross section performance. If the antenna beamwidth is kept constant, there will be varying footprint size in the range direction, due to change in slant ranges. At near off-nadir distances, the beam footprint will be smaller than the desired 30 km. Hence, in order to maintain the constant footprint of 30 km, the beamwidth is increased by switching off the TR-modules and in effect reducing the electrical width of the antenna (at near off-nadir distances). The

Fig.2.3 Distributed Antenna For h Resolution SAR Hig

Group of 24 patches fed by single TR

module in azimuth direction

Azimuth

6 m

2 m

Panel-1 Panel-2 Panel-3

Elevation 1 m

1 m

1 Tile of 24 x 24 radiating elements

2 m

2 m

pg. 21 

1.6 Selection of PRF for different Beam

positions TR-modules are switched off in the width direction, equally from outer edges of the adjacent two tiles, as shown in Fig.2.4. Hence, elevation beamwidth is varied from 2.48° to 1.67° corresponding to off-nadir distances from 100 km to 700 km, respectively, as shown in Fig.2.5. The corresponding number of active TR-module rows in the elevation direction is illustrated in Fig-2.6.

The Doppler bandwidth corresponding to antenna length of 6m and spacecraft velocity of 7.5 km/s will be 2500 Hz.

Azimuth

Elevation

6m Illuminated region of the antenna

2m

Fig.2.4: Change of Antenna electrical width to cater to variable elevation beamwidth

F ig.2.6: Variation of No. of Active TR-modules inthe width direction

Fig.-2.5 Elevation Beam-width with Beam Pointing

pg. 22 

Hence, the PRF should be greater than about 1.1 times the Doppler bandwidth, i.e. 2750 Hz. Changes in slant range corresponding to off-nadir distance change from 100 km to 700 km, lead to different echo start times and variable data windows. To accommodate the same, variable PRF is necessary. Therefore all the modes, except HRS, have PRF between 2800 – 3200 Hz. Maximum PRF is limited by the minimum data window that has to be accommodated. In the case of HRS mode, Doppler centroid estimation (for different sub-apertures) requires additional 500 Hz (over the Doppler bandwidth of 2500 Hz), therefore PRF would lie between 3000 – 3700 Hz. This large range of PRF is required to satisfy the slant range change during pitch tilting of the satellite for azimuth coverage of 100 km, for each of the off-nadir distances.

Fig-2.7 presents nomenclature related to the timing window parameters. As the slant range varies from 616 km to 928 km for off-nadir positions of 100 km to 700 km respectively, the echo return times change from 4.1 ms to 6.2 ms. Typical PRI (Pulse Repetition Intervals)

for the PRFs under consideration is about 0.3 ms. Therefore, echo corresponding to a transmitted pulse is received after certain number of pulses. The number of such pulses varies from 12 to 19 for off-nadir distances starting from 100 km to 700 km, respectively. Near margin and far margin as defined in Fig-2.7 should be more than 20μs to allow for pulse rise & fall times and sub-system switching (like, switching off the transmitter and switching on of the receiver(s), data acquisition enabling, etc.). PRF is optimized for nearly equal near & far margins within the given PRF ranges. The PRF is commandable from the ground through Payload Controller. The command is given in terms of 12-bit count corresponding to a clock frequency of 3.90625 MHz. Hence, the PRI should be an integer multiple of the

clock interval corresponding to 3.90265 MHz. Similarly, data window start time and number of data samples to be acquired are also commandable by ground commands of 12-bit and 16-bit counts, respectively. Hence, these parameters should also be integer

Start Window

Data window

No. of Pulses after which echo occurs

Pulse Width

Near Margin Far Margin

Fig.2.7: Representation of Timing Window Parameters

pg. 23 

multiples of the above-mentioned clock interval. In addition to the above requirements, the number of data samples within a data window should be a multiple of BAQ (Block Adaptive Quantization, to be described later) block size of 128.

Figures 2.8 – 2.11 present the PRF and timing window parameters for FRS-1, FRS-2, MRS & CRS modes. Best and worst case sigma naught values have been tabulated for MRS & CRS modes in Tables-2.2 & 2.3 alongwith the corresponding off-nadir values at which they occur. Fig.2.31 & 2.32 show comparison graphs for the best and worst sigma naught values for MRS & CRS mode, respectively.

Based on the above considerations, two sets of optimum PRFs have been generated for all the beam positions: 1) For all the modes, except HRS, considering a swath of 30 km 2) For HRS mode, considering a swath of 10 km.

Table-2.2

Best and Worst Sigma Naught values for

Fig: 2.8 Variation of optimum PRF with off-nadir distance

Fig: 2.9 Variation of the number of pulses after which echo is received (for (for FRS-

FRS 1 FRS 2 MRS CRS d )

Fig.2.10 Variation of data window with off-nadir distance (for FRS-

1,FRS-2,MRS,CRS modes)

Fig.2.11 Variation of timing window parameters with off-nadir distance (for FRS-1,FRS-2,MRS,CRS modes)

RISAT-1 : Orbit

The following orbit is selected

: 377

: 536.38

nation : 97.554

to-path distance : 106.3 km

RISAT-1 into 476 km

altitud

km and inclination is corrected to 97.59

with th

keeping in view, minimum number of

days for systematic coverage in MRS

and CRS mode.

Repeat cycle

orbits in 25 days

Altitude

pg. 24 

km

Incli

deg

Path-

Mean Local Time : 6 AM at

descending node

PSLV placed

e with the inclination 97.63 deg.

Orbit was raised to 536.4 km from 476

deg with a series of maneuvers. When

the spacecraft was launched, the Mean

Local Time of the orbit was 5:51 AM and

it is going to reach 6 AM around

October 2013, as there is a bias of 0.04

deg with respect to nominal inclination.

In the above orbit, ideally it takes

25 days for systematic global coverage

e same set of beams (i.e. with

same incidence angle) but, being in the

same orbit, it is possible to have global

coverage in CRS mode, every 13 days

with the same set of beams. The path

pattern for the above orbit is provided in

the diagram below.

Paths 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Days 1 14 2 15 3 16 4 17 5 18 6 19 7 20

Path pattern for the new orbit( Repeat cycle : 377 orbits in 25 days, h = 536.38 km, i = 97.544 deg )

pg. 25 

Paths 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Days 1 14 2 15 3 16 4 17 5 18 6 19 7 20

Path pattern for the new orbit( Repeat cycle : 377 orbits in 25 days, h = 536.38 km, i = 97.544 deg )

Fig.1

223 km

Path 1 Path 3Path 2

Day 1 Day 2

11 km

Day 14

106 km

212 km

115 km

Fig.2

T

he above diagram in fig.2 shows that

the images in CRS mode on two

consecutive days have overlap and with

a set of consecutive 13 days, it is

possible to have global coverage. Path -

1 is fixed at 330.3 longitude, to avoid

pg. 26 

high elevation passes over Shadnagar.

The ground track is maintained within ±

3 km with respect to the nominal

pattern. The maximum revisit time for a

given region of interest is 2.5 to 3 days

for latitudes between 20 and 40 deg.

Fig.

Fig.7

pg. 27 

Fig-6 shows the eclipse variation over a

year. It is seen that the orbit is free

from eclipse for almost 9 months in a

year and the maximum duration is 22

minutes on 21st Jun. The latitude

below which eclipse occurs on the

calendar days is shown in fig.7.

RISAT-1 : Referencing Scheme The Referencing scheme implemented

for RISAT-1 is a generalized one due to

the following factors.

SAR operates in four different

payload modes

The swath for different payload

modes can be placed anywhere

within the range between 107

km and 659 km away from nadir.

Imaging is done in both

ascending and descending passes

Roll bias of +36 degand – 36

deg are given to view on either

side of the track.

SAR is always operated in off-

nadir mode

Hence the payload trace never

coincides with the ground trace

of the orbit from which it is

operated.

The payload trace does not

follow any one ground trace, but

it crosses over many ground

traces.

With positive and negative roll

bias, the payload trace reaches

latitudes beyond ground trace

latitudes

Referencing scheme requirements

• As SAR operates in ascending as

well as descending pass, rows

over full orbit have to be

addressed

• Referencing scheme should

address scenes for different

payload modes.

• Scenes with both positive and

negative roll bias reaching

latitudes beyond the ground trace

latitude, have to be addressed.

Scheme

Nodal points are defined along

meridians and parallels

pg. 28 

The longitude range of 360 deg is

divided into 8640 points at the interval

of 2.5 arc minutes.

The latitude range of +90 deg to –90

deg is divided into 4320 points at

interval of 2.5 arc minutes.

This means that every 1deg x 1deg

grid is partitioned into 24 x 24 nodal

points. Figure – 3.3.2 shows as an

example, how 1 deg X 1deg grid with

latitude 0 deg and longitude 100 deg as

the left bottom corner, is partitioned

into nodal points.

Nodal points are addressed by four

integers i, j, m, n

i and j are the latitude and longitude

of the left-bottom corner of the 1 deg x

1deg grid to which the nodal point

belongs.

The latitude is biased by 90 deg so that

it is addressed as positive number. i

ranges from 0 to 180. 0 is –90 deg

latitude. 180 is +90 deg latitude. j

ranges from 0 to 360. and m, n range

from 1 to 24.

Partitioning of 1 deg X 1 deg grid

90,100,1,1 (lat 0.0 lng 100.0)

90,100,1,24 (lat 0.0 lng 100.9583)

91,101,1,1 (lat 1.0 lng 101.0)

91,100,1,1 (lat 1.0 lng 100.0)

90,100,24,1 (lat 0.9583 ln 100.0)

90,100,24,24 (lat 0.9583 lng 100.9583)

g

pg. 29 

X

Descending scene

Ascending sceneScene centre

c2c1

c4c3 c1

c4c3

c2

The size of CRS, MRS , FRS and HRS

scenes vary as per their swath and for

CRS and MRS mode, the total scene

with the combination of selected beams

is addressed.

• Scene framing is done in the

following manner. From the start

time, a fixed duration is

considered for each scene with

sufficient along track overlap

between consecutive scenes.

The duration for scene in each

payload mode is specified by

payload team. So, there are no

fixed latitudes for scene centres

and this avoids partial scenes in

the beginning.

• The center latitude (φ) and

longitude (λ) of the actual scenes

are identified with respect to

nearest nodal point addressed

by i, j, m, n.

pg. 30 

i = int(φ) + 90

j = int(λ)

m = int((φ- int(φ)) *24) +1

n = int((λ- int(λ)) *24) +1

For example,

φ = 1.750 deg and λ = 30.499 deg

i = int(1.750) + 90 = 91

j = int(30.499) = 30

m = (int(0.750*24)) + 1 = 19

n = (int(0.499*24)) + 1 = 12

• Also the pass type Ascending /

Descending has to be attached.

Imaging paths

As the orbit follows the repeat

cycle (377 orbits in 25 days), the

concept of path still holds good and

these are the nadir ground traces from

which imaging is done. As imaging is

done in both ascending and descending

part of the orbit, the descending ground

trace is extended on both sides (to the

previous ascending node from north

pole and next ascending node from

south pole) to get one path. Hence

there will be a break in the path number

at ascending node.

pg. 31 

pg. 32 

4.DATA RECEPTION SYSTEM

INTRODUCTION

RISAT-1 (Radar Imaging Satellite)

satellite transmits SAR (Synthetic

Aperture Radar) payload data

through X-Band carrier using dual

polarization. The data is transmitted

through one or two RF chains

depending on mode of payload

operation. The data stream of each

chain is at 320 Mbps data rate and

modulated using QPSK modulation

scheme. The bandwidth available

for data reception in X-Band is being

375 MHz, the two streams with a

total data rate of 640 Mbps are

transmitted to ground through RHC

and LHC polarized signals at X-Band

carrier frequency of 8212.5 MHz

using the frequency re-use

technique.

A new ground station has been

designed and established under the

project to cater for RISAT-1 data

pg. 33 

reception.. The ground station consists of a high efficient 7.5 m

diameter antenna system with dual

shaped reflectors in Cassegrain

configuration. A new dual polarized

feed has been designed, fabricated

and integrated with antenna system

. The station provides G/T of 32

dB/deg K. The new dual polarized

feed has been designed, fabricated

and evaluated at CATF for primary

radiation patterns and at BEL Test

range for secondary antenna

patterns

All the RF and IF subsystems of the

receive station will handle higher

bandwidth of 320 MHz. Design

implementation of individual

subsystems of ground station and the

specifications of each unit are so

drawn out that they will cater for the

required over all ground station link

margin.

Integrated Multi mission Ground

segment for Earth Observation

Satellites (IMGEOS) is being

established at NRSC Shadnagar with

an objective to have a highly reliable

and an easily adaptable system to

cater for future mission requirements

in order to achieve reduced

turnaround time for the data

product generation and

dissemination. In IMGEOS scenario,

four terminals with dual polarized S/X

band feed and identical receive chain

configuration are being established.

Two of the four terminals are currently

completed and made operational.

Data Reception Station

Configuration

4.1Station requirements to track and receive RISAT-1data

• Dual circularly polarized

X/S-Band composite Feed

• Reception of high data rate

(320 Mbps) modulated signals

• Additional LHCP chain for

X-Band Auto Track

• Synthesized Up/Down

Converter with additional

channels

• X-Band Auto Track either

through RHCP or LHCP carrier

pg. 34 

All the subsystems are designed

with provision for remote

monitoring and control capability

through Ethernet interface. Thus

all the subsystems are in a

common network configuration

,controlled and monitored through

a central station control computer.

• Auto diversityto facilitate

tracking on either of

threetracking Channels

IF Fiber optic link for

transfer of high data rate

modulatedIF spectrums.

High data rate

Demodulators at 320 Mbps (I+Q)

data rate

The Data and Tracking IF signals

from each of the four Primary

antenna systems are driven from

Concrete pedestal to Centralized

control room through Fiber Optic

links. The IF Outputs from the

Fiber optic receivers in Control

room are fed to the common

Programmable IF matrix ,which

routes these IF signals to the

respective second down converter

subsystems. The output of the

Second down converter is fed to

the Multi-mission programmable

Demodulators . The Data and clock

signals from each of the

demodulators are hard patched to

Data ingest systems.

High Data Rate RF

Simulator for simulation of RISAT-

1 RF signals

4.2IMGEOS configuration

The configuration of centralized

control room in IMGEOS

architecture is designed to meet the

automation requirements of the

data reception systems. In each of

the four primary antenna

systems, some of the Digital

Servo control and RF subsystems

are located in the concrete

pedestal , all the IF/base band

subsystems and Antenna control

computer are located in centralized

control room .

The data ingest systems are co-

located with respective

Demodulators. There will be five

dual channel data demodulators

pg. 35 

with dedicated Data ingest

systems in order to cater to

simultaneous dual carrier data

reception requirements of the four

Antenna systems, one of them being

a common redundant system .

4.3Data Reception Stationspecifications Dual shapedmain reflector :7.5 meter dia, parabolic dish Sub-reflector : 0.8 meter dia, Hyperbolic dish Frequency Range

X-Band : 8.000 to 8.500 GHz S-Band : 2.2 to 2.3 GHz

Feed : X/S band composite, Cassegrain Single Channel MonopulsePolarization X-Band : Simultaneous RHCP & LHCP S-Band : RHCP Cross pol. Isolation :20 dB

Antenna gainX-Band: 54dBi

S-Band: 40 dBi G/T X-band : 32 dB/ºK @ 5º EL S-Band : 16 dB/ºK @ 5º EL

Half power beam width X-Band : 0.27º S-Band : 1.1º

Type of mount :

Elevation over Azimuth

Fig. 3 IMGEOS Configuration of Data Reception Station

Maximum Velocity : AZ- 20º/sec , EL- 10º/sec

Maximum accélération :

AZ- 10º/sec² , EL- 2º/sec²

Data rates : 320 Mbps (I+Q) in each chain

Tracking : S/ X (R) /X (L) AutoTrack

Program Track as back-up

Threshold Eb/No :13.3 dB for 1X10-

6BER

4.3.1Brief description of Data Reception Station

pg. 36 

The station consists of a dual

shaped antenna system with a

7.5 m dia parabolic reflector.

The dual shaped antenna along

with feed in

Cassegrainconfiguration provides

G/T of 32 dB/º K. The composite

S/X feed is dual circularly

polarized in both S & X

bands.with the capability to

receive LHC and RHC polarized

signals simultaneously.

The antenna and feed system is

mounted over an EL over AZ

drive pedestal. The feed and

front-end system realizes single

channel monopulse tracking. The

X-Band data is received through

RHCP and LHCP

simultaneouslyusing frequency

re-use technique.

The X Band data and tracking error

signals from RHCP & LHCP chains in

identical configuration are amplified

in LNA and down converted toa first

Intermediate frequency in the range

of 2.2 to 2.9 GHz IF. The S-band

Telemetry Data and Tracking signals

are down converted to 70 MHz IF.

The down converted X and S band

tracking IF signals are fed to a

three channel Integrated Tracking

system (ITS), located at antenna

pedestal. The ITS demodulates the

tracking IF signal and extracts AZ

and EL DC error information from the

tracking video. The DC errors are

fed to Digital Servo System to

control the antenna movement for

satellite tracking in Auto Track mode.

The Digital Servo System

comprises of Antenna Control

Computer, Drive Power Amplifiers

Drive motors and Optical shaft

Encoders to operate the Antenna in

different modes of operation viz,

Rate mode, PTS mode, command

angle mode and Auto mode . The

System has provision for remote

control and configuration through

Ethernet interface

The Drive system consists of Power

Amplifiers, Brush less DC motors, Gear

boxes (Dual drive mode) and Slew-rings

pg. 37 

in each El. and Az, axis. Each axis is

driven by two motors in counter torque

mode to avoid backlash. Absolute

optical shaft encoders are used for

measuring the angular position of the

antenna. All safety interlocks are

provided in the drive system.

The IF outputs from first data down

converter (2 carriers) and S band

data IF are driven to the control

room through a multi-core optical

fiber cable. The S band Data IF is

driven to SPS receiver in control

room for further processing of SPS

Data.

The twodata IF signals received

in control room are fed through

programmable IF Matrix to the

second down converter and then to

High data rate digital demodulator.

The data and clock signals from

demodulators aredriven through

LVDS interface to Data Ingest

System for further processing and

product generation. The total data

acquisition system for all the

Antenna Systems are automated

through Station Control Computer.

4.4Detailed Functional Reception of

Data Reception station

The data reception station comprises

of the following major systems. The

functional block diagram of data

reception station is given in fig 2.

• Antenna &Tracking Pedestal

• Dual Polarized Feed& RF systems

• Digital Servo & Automation

system

• IF &Base-Band system

• Data Ingest System

The detailed functional

description and specifications of

each of the subsystems is given

in the following sections.

pg. 38 

Fig.4 Data Reception Station

block age and sub reflector spill

over, which significantly affect the

gain of the antenna. The main

reflector consists of a machined,

reinforced circular hub, which

supports 16 radial trusses and

other interconnecting braces.

The 16 trusses support 16 solid

surface reflector panels. Aviation

warning lights and lightening

arrestor are mounted on the

reflector. Sub reflector is

4.5 Antenna &Tracking Pedestal

4.5.1 Antenna

The reflector is a 7.5-meter

diameter Parabolic Antenna with a

focal length to diameter ratio (F/D)

of 0.41. The focal length of the

reflector is 3.07 meters. The sub

reflector diameter has been

selected as an optimum value in

the trade-off between reflector

pg. 39 

4.5.3Drive chain hyperboloid supported by four

aluminum quadri-pods. Antenna

mounting frame attaches the

reflector to a pair of Yoke arms

with Counter weight arms.

The drive chain is a dual drive

system in both Azimuth and

Elevation axes, using brush less

DC motors to enhance the

reliability and performance. The

drive system is configured with

precision anti backlash gear

system and torque bias

arrangement to provide better

tracking and pointing accuracies.

All the four drive motors are

identical with integral

tachometer, resolver and brakes.

The brushless DC servo motors

are coupled to the output axis by

means of a high efficiency gear

reducer and torque coupling.

4.5.2 Pedestal

The pedestal system is an

Elevation over Azimuth mount

type. The Elevation housing

contains the necessary drive

system for antenna movement

about an Elevation axis between -

2° (below the horizon) to zenith

and Azimuth housing containing

the drives to achieve ± 360°

rotation about the Azimuth axis.

The Azimuth housing (Fig.)

consists of a fabricated

stiffened cylindrical steel drum

supported on a concrete

pedestal. The Azimuth drive

mechanism is housed inside it.

The Pedestal assembly consists

of drive components, gear

boxes, optical encoders, Electrical

limit switch assembly and Stow

lock motors.

A cable wrap system will be

provided in the pedestal housing

to protect the cable elements

from damage due to uncontrolled

cable twist loops, during the

antenna movement.

4.5.4Azimuth housing

The Azimuth Slew ring bearing is

supported at the top of the Azimuth

housing which is properly machined

pg. 40 

to match the Slew ring bearing

surface and attached to it using high

strength bolts. The Azimuth housing

is connected to Elevation housing

using high tension bolts fitted to

inner ring of Azimuth Slew ring

bearing.

4.5.5Elevation housing

The Elevation housing (Fig. 4) is

a structure fabricated out of

steel plates. It houses the

elevation drive mechanism. The

bottom of the Elevation housing is

machined to suit the fixed part of

the Azimuth Slew ring bearings

and is fitted to it by high tensile

steel bolts. An access is provided

in the Elevation housing for routing

cables through the hatch. The Yoke

arms are attached through Slew ring

bearings to Elevation housing. The

Physical structure of the antenna

with details of complete mechanical

components of the pedestal

assembly is shown in fig.3.

Fig.5 5m Dia. Antenna System

pg. 41 

4.7Technical Specifications: Pointing Error : 0.08° peak Operating Temperature : 0° C

to 55° C Antenna Type : Parabolic

reflector Wind Speed Diameter Main Reflector :

7.5 meter shaped parabolic solid

dish

(a) Operational wind speed

: 60 Kmph

(b) Occasional gusting : 80

Kmph Sub-reflector : 0.736 meter

Hyperbolic dish ( c)Drive to stow : 100 Kmph F/D : 0.41 (d) Survival wind speed in Zenith

: 200 Kmph Focal length : 3.077 meters

FeedConfiguration :Cassegrain Natural resonant Frequency :

4 Hz S Band : 8 Helices

X-band :4 Conical dielectric

elements Weight : 1.4 Tons

4.8Dual Polarized S/X Band Feed &RF Systems

Overall RMS

(a) Main Dish : 0.5 mm

RMS

4.8.1Dual Polarized S/X Band Feed (b) Sub-reflector : 0.05

mm

The feed is of multi-element Single

channel mono pulse tracking type,

capable of receiving dual circularly

polarized S & X-band signals. The

feed comprises of an array of 4

conical radiating elements designed

for simultaneous reception of

RHCP&LHCP X-band signals and an

array of 8 helical elements, 4

elements for reception of RHCP & 4

elements for LHCP signals in S-

Sky coverage

(a) Elevation : 2°to182°(Mech),-

0°to 180° (Electrical)

(b) Azimuth :±360°Velocity

(a) Elevation Axis : 10° / sec.

(b) Azimuth Axis : 20° / sec.

Angular Acceleration

(a) Elevation Axis

: 2° /sec2

(b) Azimuth Axis : 10° /sec2

pg. 42 

band. The feed array inmono pulse

configuration receives offset

beams corresponding to Azimuth

and Elevation axes in both Right

Hand Circular and Left Hand

Circular Polarizations .

The septum polarizer receives the

signals from feed elements of X

Band and provides linear polarized

signals corresponding to RHC and

LHC signals. The linearly polarized

signals are in turn fed to a wave

guide mono pulse comparator to

generate sum and difference

signals. The feed elements are

assembled on a cylindrical shroud

and covered with a radome casing

which gives environmental

protection. The shaped antenna

system together with the RF front-

end system realizes a G/T of better

than 32 dB /deg. K at 5 deg.

Elevation in X Band.

The antenna has highly directive

pattern with half-power beam

widths of 0.27 ° in X-band and 1.1°

in S-band. The feed elements are

arranged to produce two beams

which are offset in AZ plane, and

two beams offset in EL plane .The

feed assembly also contains

waveguide Mono Pulse Comparator

(MPC)and Mono Scan Converter

(MSC) for RHCP and LHCP chains

in X-band and micro stripline

MonoPulse Comparator and Mono

Scan Converter (MSC) for S-band.

The Mono Pulse Comparator

compares each pair of beams to

produce the tracking error signals,

when the antenna RF axis is exactly

on Boresightaxis , each beam has

equal amplitude and their

comparison results in zero signals in

difference port. The sum channel is

formed in the MPC by adding all

four beams together. The AZ and

EL error signals coming out of

the MPC are given to MSC,

which carries out time division

multiplexing such that the

Azimuth and elevation tracking

error signals are combined in to

pg. 43 

a single channel tracking signal ,

with reference to the Azimuth-

Elevation Scan pulses and 0°, 180°

phase scan pulses which are

driven from Integrated Tracking

System to the feed. In case of X-

band, these pulses are routed

through driver card in RF junction

box. Fig.4shows the functional

block diagram of dual polarized

feed.

.

Fig.6 Block diagram of dual

polarized feed

The received signals in X-Band are

passed through 30 dB test loop

coupler and amplified in low noise

amplifiers. The loop coupler is used

to introduce the test signal in the RF

chain to evaluate the system

performance in Local loop simulation

mode. The amplified outputs are fed

to 2 way in-phase power divider.

One output of power divider is taken

out as Sum/Data signal and applied

to X-band down converter to

generate Data IF. The other output

of power divider is combined with

the Single channel tracking error

signal to generate the Amplitude

modulated tracking Signal, which is

then down converted to generate

tracking IF.

pg. 44 

The input X-band sum signal is

divided by a power divider to

provide two outputs.

4.8.2Feed specifications

Type : Cassegrain feed One output is used for data and the

other output is given to a 6 dB

coupler, where amplified error signal

is coupled for generation of tracking

error signal. The X- band

directional coupler is a 6 dB

strip line type with SMA coaxial

connectors. It has minimum insertion

loss and good directivity.

Frequency Range X-Band : 8.000 to 8.5 GHz S-Band : 2.2 to 2.3 GHz Polarization X-Band: RHC & LHC S-Band: RHC & LHC Half power beamwidth X-Band: 0.27º Before getting coupled with sum

signal, the difference signal at the

input is passed through a digital

phase shifter in order to compensate

for phase mismatch between sum

channel and difference channel. The

phase shift is digitally controlled

using 6 bit TTL signals, driven

from Integrated Tracking System.

The step size of minimum phase shift

is about 5.6° . These 6 bits can be

optimized and programmed to

facilitate tracking through any

carrier frequency over X-Band

frequency range.The phase match

can be adjusted periodically if

required through local or remote

control.

S-Band: 1.1º

Side lobe level : 14 dB Null depth : Better than 25 dB Axial Ratio : 2.0 dB max

4.8.3X-Band DPC (Divider, Phase

Shifter, Coupler) The X-band sum and error signal

amplifier outputs of both RHC and

LHC signals are fed to the input

ports of DPC. The unit has two

independent channels to provide

tracking and data signals of RHC

and LHC chains.

pg. 45 

The DPC subsystem comprising 2

way power divider, digital phase

shifter and a 6 dB directional coupler

is wall mounted in pedestal room.

4.8.4 S-Band DPC

The S-Band DPC has a single

channel to process RHC signals. and

the rest of the configuration and

function are the same as that of X-

band DPC.The S band Data signal is

driven to the control room for further

processing of SPS data after down

conversion to 70 MHZ.

4.8.5 X- Band Up/Down Down Converter

The up/down conversion of X-Band

signals is based on dual conversion

technique.The received X-Band

signal in the frequency range 8000-

8500 MHZ is converted into first

IF signal in the range 2345-2845

MHzduring first conversion, by

mixing with a fixed local oscillator

signal at 5655MHz.

In the second conversion, the first IF

signal beats with a local oscillator

signal derived from frequency

synthesizer. The frequency of built-in

synthesizer is programmable over

the range 1560-2185 MHz in order

to derive the desired Intermediate

Frequency of 720 MHz and

facilitate multi mission data

reception. The frequency

synthesizer is controlled and

monitored through TCP/IP remote

interface.

4.8.6 X-Band Down Converter

The data and tracking down

converters, each consists of two

identical channels to support LHCP

& RHCP chains for the first

conversion. The data and tracking

down converters are housed in

separate boxes and they are

located at antenna pedestal.

The second down converter for

tracking is located at pedestal.

The second IF output of tracking at

720 MHz is fed to Integrated

tracking system for extraction of AZ

and EL DC error signals and

drive the digital servo system. The

second data down converter unit is

pg. 46 

co-located with demodulators in

control room.

4.8.7X-Band Up Converter

Up-converter is used to convert

desired IF signal at 720MHz to a

suitable first Intermediate frequency

in the range 2345-2845 MHZ in

first conversion unit and

subsequently converted to

desired X-Band signal frequency in

the range of 8000-8500 MHz in the

second conversion unit of up-

converter.

The first up-conversion unit is

located in the control room and

the outputs of up-converter are

compatible to both bore sight

system and local loop simulation.

The second up-converter unit for

Local Loop is located at

pedestal and that of Boresight

system is located at Boresight

room .The selection for routing of

the up-converter output between

bore sight and local loop is

carried out through remote

interface.

4.8.8 S-Band Down converter

The S-Band Down converter is

based on single conversion. The

down converter consists of two

identical channels to support data

and tracking. The received S-Band

data and tracking IF signals in the

range of 2.2 to 2.3 GH z are down

converted to a 70 MHZ IF. The L.O

signal for down conversion is

derived using a programmable

frequency synthesizer module.

4.8.9Integrated Tracking System

The S tracking IF at 70 MHz and X

band (R&L) tracking IF signals at

720 MHzfrom corresponding down

converters are fed to Integrated

Tracking system (ITS). The ITS

demodulates AM tracking video from

IF signals. ITS works in non-

coherent mode and the AM video

detection is achieved by simple

envelope/peak detection method.

ITS has built-in Automatic gain

pg. 47 

control modules to provide constant

amplitude signal and DC errors for

varying input signal leevls. The AGC

bias signal is also provided as an

output signal for facilitating auto

diversity reception and auto

acquisition.

Two Spectrum analyzers are required

for real time monitoring of the X

band data and S band tracking IF

signals and for carrying out regular

maintenance of the receive chain.

ITS has auto diversity reception to

select any one of the two (In case of

both S & X –band inputs) input

signals being present, based on their

signal strength (AGC). ITS uses

separate error demodulator modules

in both Elevation and Azimuth axes

to extract dc error. ITS unit also

consists of a Scan code generator

module which generates two sets of

Scan pulses. One set of Pulses called

AZ-EL scan pulses are of 1 KHz

frequency and the other set called

Phase scan pulses are of 500 Hz

frequency. These pulses are

simultaneously applied to the

Monoscan converter module in the

Single channel monopulse feed and

used in the tracking demodulator

circuits in both Elevation and

Azimuth channels for synchronizing

the process of Error generation and

demodulation.

The Azimuth and Elevation DC

output errors are applied to the

Servo system for driving the antenna

towards the target position and to

nullify the tracking errors. ITS has

provision for adjustment of various

parameters of the tracking chain like

Phase shifter adjustments, DC offset

error gradient and Acquire /Loss

threshold.

4.9IF and Base Band Systems

4.9.1Programmable IF Matrix

The Programmable 4X4 (RHCP )

4X4 (LHCP) IF Matrix facilitates

automated inter connectivity of IF

signals(Output of first down-

converter) from different Antenna

Terminals to the input of the Second

pg. 48 

down-converter followed by the

Demodulator. The main function of

the IF matrix is to facilitate total

automation of the data reception

chain including the IF signal path

routing. IF Matrix also eliminates

the problems associated with

manual patch panel like, loose

contact problems, mechanical

wear and tear of the patch chords,

operator errors etc., thereby

improving the reliability of the

system ,while increasing the

flexibility and reducing the

complexity.

4.9.2IF Fiber Optic Link The first IF signal in the range of

2345-2845 MHz from the output

of 1st down converter is driven

to control room through Fiber

Optic link. The Fiber optic

linkcomprises of fiber optic

transmitters and receivers. The

transmitters are placed at the

Pedestal end and the output of

transmitter is driventhrough a

Single mode multi core fiber

optic cable. The Fiber optic

receivers are placed at the

controlroom to receive the

signals. The two downlink data IF

signals corresponding to RHCP

and LHCP, two uplink data IF

signals and S-Band data IF

signals are driven through F.O

link from pedestal to control

room.

4.9.3High Data Rate Demodulators

The down converted IF signals of

data channels passed through

band pass filters. The pass band

of band pass filters is 320 MHz

with minimum group delay and

good rejection characteristics.

The filtered signal levels are

amplified in IF amplifiers so that

the boosted levels are within the

dynamic range of demodulators.

The multi mission High Data

Rate Receivershave the

capability to receive and

demodulate QPSK signals of

RISAT, which are modulated at a

very high data rate of 320 Mbps.

The demodulator and bit

pg. 49 

synchronizer are supported in a

single unit. The unit receives

QPSK modulated signals at 720

MHz IF and provides

synchronized data and clock

signals as outputs. The LVDS I

and Q output data and clock

signals arefed to Direct Ingest

System (DIS) for further

processing of data. The

Demodulator unit has the feature

of supporting any data rate

continuously variable from 1 to

320 Mbps.

• Monitoring & Control of

through TCP/IP

• Automated/unmanned

tracking operations

• FO link for remote operation

of ACSS

• Built in Test & calibration

software for comprehensive

maintenance

Specifications: Tracking Velocity :

20 deg/sec in AZ, 10deg/sec in EL

Tracking Acceleration : 10 deg/sec² in AZ, 2 deg/sec² in EL

4.10 Digital Servo Control System

Servo pointing accuracy : < 0.03 deg

Position display Resolution : 0.001 deg The Servo Control System has all

the salient features of modern

digital control system available in

any of the latest ground stations,

using the state of the art

technology. The main features of

the system are

Position Transducer :19 bit or higher, single turn

Absolute rotary shaft optical encoders

Position loop bandwidth : Tunable from 0.1 to 2.0 Hz

Rate loop bandwidth : Tunable 1.0 to 10.0 Hz

Operating modes : Standby, Slew, Manual, Program, • DSP based Antenna Control

Unit Designate,X-Auto,S-Auto,Sun/Star, Auto sequence mode • Software based digital

control loops Type of motor/drive :

• Zenith pass handler

pg. 50 

Brushless AC servo motor with Resolver feedb

ack and built

in brake/PWM drive 4. Tracking & Control

software Drive configuration : Two motor Counter-torque Secant correction : Azimuth axis through software

4.11Antenna Drive Unit System Control Options :

Local/Remote

The ADU houses the DC servo

drive unit that includes 4 Pulse

Width Modulated (PWM) servo

amplifiers to drive the azimuth

and elevation Brushless DC servo

motors. Two motors are used for

each axis.

The Servo Control System has the

following sub systems. The

complement of above equipments

shall provide a wide variety of

operating modes for the antenna.

The block diagram of servo control

system is shown in fig 4. The drive unit operates as a

current / torque loop with torque

bias set by the ACU to minimize

backlash and maximize pointing

and tracking accuracy. The

torque bias parameters are

configurable in the ACU to

optimize performance.

1. Antenna control unit (ACU)

2. Antenna drive unit (ADU)

3. Tracking Network

configuration

pg. 51 

ADU contains drive amplifiers and

logic for azimuth and elevation

axes control, power on sequence

and safety interlocks. The ADU

also provides power and interface

points for the discrete I/O

antenna points. The ADU includes

all the required power supplies

for drive amplifiers, drive

electronics, switches, stow pins,

alarms and motor brakes. These

status points are controlled and

monitored by the ACU. The

additional protections built into

the drive systems are bus

under/over voltage protection,

short circuit protection, Over

Temperature (Heat sink)., Over

current trip, Electronic fusing,

Resolver connection fault (open

circuit).

4.11.1Antenna Control Unit

The Antenna Control Unit (ACU),

along with the Antenna Drive

Unit, is responsible for closing the

position loop, reading the

position sensors, commanding

the Antenna azimuth/elevation

Drives. The ACU contains the

hardware and firmware to close

each axis position loop with the

position feedback from the on

axis position transducers (optical

rotary shaft encoders). The

sources of the position

commands shall, apart from

internally generated, include

tracking receiver generated error

signal. The generated position

error is frequency compensated

and converted to rate commands.

For the full motion control, the

rate command is compared with

the motor rate feedback. The

error is then used to control drive

amplifiers that effectively apply

armature supply to the brush less

DC servomotors. The ACU

provides all manual and

automatic target acquisition and

antenna positioning functions.

The ACU communicates with the

drive system and Ethernet

through TCP/IP protocol. ACU

issues drive enable commands as

well as to read the various status

parameters from Drive system

through this interface.

pg. 52 

The Antenna Control servo

system shall have extensive

operational modes to meet the

antenna requirements for orbiting

satellites. The system shall have

two operating control

environments. One is “Local mode

(operator control)” from Remote

Fig.7 Block Diagram of servo

control system

4.12Tracking Network Configuration

antenna control computer (ACC)

at Control room or Antenna

Control Unit (ACU) at Antenna

pedestal room and another is

“Remote mode” via Station

Control Computer (SCC) system

from Earth station control room.

The operating modes supported

by ACU are Standby, Ready,

Manual Position, Slew Rate,

Command angle , Auto track (X-

band & S band) and Program

Track.

The primary operational interface for the

Antenna control servo system is the

Remote Antenna Control Computer

(RAC), which provides remote control of

the

 

E

E

AZ Axis

EL Axis

Drive

Delta Tau UMAC Motion

Controller

EL absolute encoder & limit signals

AZ absolute encoder, cable wrap & limit

GPS Timing Signal

S-band Signal

Generato

Other I/O

Signals

Integrated

Tracking

ACU Computer

Down Converter

Drive

Drive

Drive

Etherne

Ethernet Switch

RS-232 RS-232 Etherne

Analo

RAC

Fig 5: Block Diagram of servo control system

pg. 53 

Antenna control unit (ACU) from

the Control room. The Remote

antenna Computer (RAC)

communicates with the Antenna

Control Unit (ACU) over

dedicated Fiber optic link.

The ACU communicates with the

drive systems of both azimuth

and elevation axis through

Ethernet. ACU issues drive enable

commands to the drive system as

well as monitor the status of the

drive system through this

network. The other important sub

systems like Integrated Tracking

System, Multi channel tracking

down Converter etc. are

connected on the same network.

The typical network configuration

is shown below.

pg. 54 

Tracking Down

Converter

Integrated Tracking System

Antenna Drive System

Antenna Control Unit

Antenna Pedestal Switch

FO Link

DRS LAN Switch

Fig.8 Tracking Network Configuration

4.12.1Station Automation System

The purpose of the station automation

system is to operate

the ground station in a fully

automated environment aiming

towards unmanned operations.

The main functions of the Station

automation are carried out by

Station Control Computer in

coordination with Antenna

Control Computer.

pg. 55 

Fig.9 Station Automation

System Configuration

NRSCground

station has four antenna systems

and five data receive chains and

its configuration is shown in

Figrue-6. The Antenna Systems

are located in the

Antenna Pedestal room and its

purpose is to track satellite in

auto or program track mode.

These antenna systems are

controlled from the Data

Acquisition Control Room (DACR)

by Remote Antenna Control

Computer (RAC) through Servo

Fiber optic (SFO) link.

The 2 GHz Data output from the

antenna system is driven by

another Fiber Optic link DFO to

bring to the DACR. These

outputs from all four antenna

systems are routed through IF

Matrix to connect it to different

Data Receive Chains. Each Data

Receive chain has two streams to

support IRS-P5, Resourcesat-2

etc. Both the streams are

configured to same in case of

Single stream missions like

Carotsat-2/2A, Oceansat-2 etc.

pg. 56 

4.13Station Control Computer

Station Control Computer carries out the

automation of IF matrix and Data

receive chain and its configuration

diagram shown in Figure-7. Each data

receive chain has one down converter

and one demodulator. These systems

are connected on Two 24 Port Ethernet

Switches.

Fig.10 Devices connectivity of Station Control Computer

The software is developed with the

following features to carry out the above

functions

• It facilitates highly

configurable environment

which is adaptable to addition,

deletion or change in

configuration parameters in

various configuration file.

• All the independent modules

are made to run on different

threads. This helps in running

other modules smoothly when

a particular module faces

some problem.

pg. 57 

• Two TCP/IP application level

protocols are developed for

message passing between

SCC and various ACC systems.

One for SCC server to ACC

client and the other for ACC

server to SCC client.

pg. 58 

5.LEVEL’0 SYSTEMS • Data Ingest and Quick Look

Display System 5.1Introduction • Ancillary Data Processing System

• SPS PB Data Archival System RISAT-1 is the first Microwave Indian

Remote Sensing Satellite. It carries an

Active Microwave payload SAR

(Synthetic Aperture Radar) operating in

C-Band, enabling data collection in

Day/Night and all weather conditions.

The Ground Segment comprises the

Data Reception, Processing &

dissemination facilities. The following

sections describe the various sub-

systems of the Level-0 Systems for

RISAT-1.

• Data Serializer System

• Timing System.

Level-0 Systems will be realized in

IMGEOS Configuration. Each of the

FOUR antenna and Data Receive Chains

have a dedicated Data Ingest System

(Shown in Figure 8) for real-time data

ingest onto RAID and subsequent

transfer to SAN for ADP Processing.

Based on clash scenario Two antenna &

data receive chains will be assigned for

RISAT-1 as Main & redundant chains. Level ‘0’ Systems

• Station Work Flow Manager for

Event Scheduling and Monitoring

pg. 59 

IF MATRIX

AS - 1 AS - 2 AS - 3 AS - 4

DEMODULATOR 1 DEMODULATOR 2 DEMODULATOR 3 DEMODULATOR 4

Data Ingest System 1 Data Ingest System 2 Data Ingest System 3 Data Ingest System 4

Fig.11 Data Chain Configuration

5.2 Station Work Flow Manager

Station Workflow Manager provides

centralized event monitor and control

functions for Station operations with

appropriate interfaces with UOPS for

pass schedules, state vectors, and

Urgent/Emergency requests. On receipt

of Pass Schedules for a Day, SWFM

generates Work Orders for Station

Control Computer System for

assignment of Antenna Systems &

Receive Chains. It also generates WO

for the respective Data Ingest Systems.

On receipt of successful data ingest

message post pass from DI, Work

Orders are issued by SWFM for the ADP

Processing Nodes. Event Monitor &

Controller displays Process status and

provides control for Process initiation,

restart & abort.

pg. 60 

Pass Schedules / UrgentRequests / SVs

Data Exchange GatewayU O P S

Station Work Flow Manager

Data IngestSystems ADP Systems

W O Files

RAW Data ADIFFRED

Fig.12 Station Work Flow Interfaces

5.3Data Ingest System The Data Ingest systems consist of PC

servers with RAID for real-time data

ingest. 2 Nos of PCI Front End Hardware

(FEH) Cards which are connected to the

Demodulators with LVDS interface.

IRIG-G Time is fed to the Time Code

Translator which translates the serial

time and provides parallel BCD Time to

FEH for time stamping the Raw Data.

TCT provides RS-232 I/F for system

time synchronization.Data Ingest

System gets work orders from SWFM,

schedules the supported passes,

acquires real-time data, provides a real-

time display of important parameters

like Sync Status, FS Errors, GRT & Line

Count Jumps, etc. After the completion

of LOS, RAW data acquired in RAID is

transferred over FC network to SAN

along with the quality report.

Appropriate Event Message indicating

the status of data acquisition is sent to

SWFM for further initiation of ADP

Processes.

pg. 61 

RAIDLEVEL-0 SAN

Data Ingest Server

4 Gbps FC Link

SWFM

DI Work OrdersStatus Messages

FEH card 1

FEH 2

PCI (64 BIT, 66 MHZ)

PCI (64 BIT, 66 MHZ)

Stream1

Stream2

FEH 1

PCI (64 BIT, 66 MHZ)

PCI (64 BIT, 66 MHZ)

Parallel BCD time I/F

Stream2

DEMODULATOR

LVDS/ECL

LVDS/ECL

TCT

IRIG - G Fig.13Data Ingest System Configuration

5.4Timing Systems The NTP server port on the Unit is

used for accurate system Time

synchronization. Serial IRIG-G

time code from XLI unit is fed to

the Serial Time Distribution Unit,

which buffers and provides the

Serial Time to the Time Code

Translators on Data Ingest

Systems.

Station Timing Systems consist of

XLI Time and Frequency Unit (NTP

Server), Serial Time Distribution

Unit and Time Code Translator

Units.

The XLI Time & Frequency System

has 12-channel GPS Receiver, GPS

synchronized Time Code

Generator, high precision rubidium

oscillator for clocking the TCG.

pg. 62 

GPS Antenna

Serial Time Distribution Unit

IRIG-G

TCT 1 TCT 4TCT 2 TCT 3

NTP Time Unit

N/W SwitchNTP Time

Fig.14 Timing System Block Diagram

5.4.1IRIG-G Time Code Translator

Serial Interface provides the ASCII

time for System time

synchronization and scheduling of

events. The Set-time and Read-

time Utilities are provided for off-

line configuration of the system

and validation of the interface

respectively. Displays DAYS:

HOURS: MINUTES and SECONDS

on the front panel.

IRIG-G TCT has been developed

in-house for meeting the GRT time

stamping requirements of RISAT-

1. The TCT accepts IRIG-G Serial

Time Code and translates it into

Parallel BCD format up to 10

Microseconds to Front End

Hardware (through 68 Pin SCSI

connector) for Time stamping the

RAW data being ingested. The

pg. 63 

AGC Logic DECODER

SCAN LOGICMINOR FRAME SECTION

MAJOR FRAME SECTION

BCD TO 7 SEGMENTDECODER / DRIVERS

68 PIN SCSI Connector /50 PIN Centronics Connector

IRIG -GMODULATED SIGNAL

IRIG ADC CODE

Dec

oded

Par

alle

l BC

D C

ode

Parallel BCD Data

1 PPS Clock

Frame Sync

Load Pulses

7-SEGMENT DISPLAY

Fig.15Time Code Translator

pg. 64 

6.SAR Payload for RISAT

Radar backscattering depends

upon the sensor parameters such

as frequency, polarisation and

incidence angle as well as on

target parameters such as

dielectric constant, roughness and

geometry. In RISAT, SAR sensor is

selected in C-band (5.35 GHz)

with both co- and cross-

polarization, which will meet most

of the resource applications and

also enable achieving high

resolution capability. The SAR

sensor is based on active phased

array antenna technology, which

will provide requiredelectronic

agility for achieving multimode

capability.

6.1Modes of Operation

The RISAT High Resolution SAR

will be operating in C-band at a

frequency of 5.35 GHz. The

spacecraft altitude has been fixed

at 536kmfrom the 25-day

repetivity considerations. The SAR

system has beendesigned to

provide constant swath for all

elevation pointing and almost

near constant minimum radar

cross section performance. The

proposedSAR will operate in the

following basic modes: Figure-

15&Table-1

Fine Resolution Stripmap

Mode-1 (FRS-1): This mode is

basedon Stripmap imaging, which

is the conventional mode of SAR.

In this,the orientation of the

antenna beam is fixed with

respect to flight pathso that a strip

of constant swath (here, 30 km) is

illuminated along theflight

direction. The intended resolution

is 3m for FRS-1 mode.

Coarse Resolution ScanSAR

Mode (CRS): The ScanSAR mode

allows for a multifold increase of

the range swath dimension. This

isachieved by periodically stepping

the antenna beam to the

neighboringsubswaths (in the

range direction). In the CRS-mode

of RISAT, therewill 12 beams

(either side of the intermediate

sub-swaths will have anoverlap of

pg. 65 

High Resolution Spotlight

Mode (HRS): In the spotlight

mode,

7km from the preceding and

succeeding sub-swaths). This

results, total swath in CRS mode

would be 220 km. the resolution the antenna beam is oriented

continuously to illuminate a

particularspot on the ground. This

way, the target aperture time is

increasedwhich results in

improved azimuth resolution

(compared to that in thestripmap

case) which will be 1m for this

mode. The improved resolution

offered in this mode will be 50 m.

Medium Resolution ScanSAR

Mode (MRS): This is a 6-beam

scanSAR mode, similar to the CRS

mode, providing a resolution of 25

m over a swath of 115 km.

Fine Resolution Stripmap

Mode-2 (FRS-2): This mode has

quadpolarization capability.

Philosophically, this mode is a

hybrid strip mapand scanSAR. It is

stripmap in the sense that the

beam orientation iskept fixed with

respect to the flight path and a

strip of constant swathwidth is

covered. Also, in a way it is similar

to scanSAR, because forpart of

the aperture time the beam

polarisation is switched from

Vtransmitto H-transmit, and vice-

versa. Hence, this mode would be

is obtained at the cost of azimuth

coverage. The latter is

partlyimproved by making use of

sliding spotlightmode (hybrid

spotlightstripmapmode). This

imaging would be done over a

spot size of 10 kmx 10 km.

Circular Polarimetric Modes

(C-HRS, C-FRS-1, C-FRS-2,

CMRS,C-CRS): All the modes

mentioned above can be operated

inhybrid-circular polarization. This

is achieved by transmitting H & V

used for polarimetry, as we can

have all the four combinations of

polarized signals simultaneously

but with a relative phase-shift of

90°.Hence, the transmit signal is

in circular polarization and the

receivesignal is in linear (dual-pol)

polarisation, viz, VV, VH, HH &

HV.

pg. 66 

– this makes it a hybrid-

circularpolarization operation. To

keep the average power-

requirements sameas the original

specifications, the pulse-width is

reduced to half.

FIGURE-15 Basic modes of SAR

Fig.16 Non Imagable area

Except FRS-2 mode, which is

inherently quad pol mode, all

othermodes can be operated

either in single polarization modes

(HH, VV,HV, VH), dual polarization

modes (HH+HV / VH+VV) or

Circularpolarization modes.

Also it shouldbe remembered that

as it is a side looking active sensor

around 107 Km either side of the

Sub satellite Track comes under

Non Imagable area for that orbit

under consideration.( Figure 14)

Fig.17 Basic Mode of SAR

Antenna Pedestal Room

pg. 67 

Table.2 Payload Modes

DRS Systems

7.RISAT DATA PRODUCTS & FORMATS

pg. 68 

Radar Imaging Satellite (RISAT-1) will acquire data in C band with following modes:

Geo-Tagged Products (Level-1) :The image is geo-tagged using orbit and attitude data from the satellite. This allows latitude and longitude information to be calculated for each line in the image. The earth geometry is assumed to be the standard ellipsoid. Each image line contains auxiliary information which includes the latitude and longitude of the first, mid and last pixels of the line. The raw radar signal data is processed to provide SAR image data pixels. The image pixel data is represented by a series of CEOS processed data records, each record containing one complete line of pixels lying in the range dimension of the image. The product can be obtained as slant range data (16 bit I and 16 bit Q) or ground range data (16 bit) amplitude data. Additionally, an auxiliary file containing a dense grid of geo-locations is associated along with the data file.

• Fine Resolution Strip map Mode-1 (FRS-1): It provides 2 m slant resolution image over 25 km swath in either single or dual polarisations

• Fine Resolution Strip map Mode-2 (FRS-2): It provides 4 m slant resolution image over 25 km swath in quad polarisation.

• Medium Resolution ScanSAR Mode (MRS): It provides 8 m slant resolution image over swath of 115 km in either single or dual polarisation

• Coarse Resolution ScanSAR Mode (CRS): It provides 8 m slant resolution image over swath of 223 km in either single or dual polarisation.

• High Resolution Spotlight Mode (HRS): It generates better than 1 m resolution image fora spot of 10 km (Azimuth) and 10 km (ground range swath) for either single or dual polarisation.

7.2Ellipsoid Geocoded Products (level-2) : This product contains geometrically corrected data. There exists provision for UTM (default) and Polyconic map projections. For systematic processing UTM projection will be provided. The pixel spacing in the product will depend on mode, no. of looks and look angle. For a given mode and a range of look angle, no. of range and azimuth looks will be worked out in such a way that pixel spacing in both range and azimuth direction remain uniform. The options for product format are CEOS and GEOTIFF.

The various levels of products defined for RISAT-1 are as follows: 7.1 Raw Signal Products (Level-0):This product contains raw or unprocessed radar echo data in complex in-phase and quadrature signal (I and Q) format. The only processing performed on the data is the stripping of the downlink frame format, BAQ decoded (optional) and re-assembly of the data into contiguous radar range lines. Each range line of data is represented by one Signal Data Record in the RAW CEOS product. Auxiliary data required for processing is also made available along with echo data.

7.3Value added products: Beside the above mentioned standard data products, additional products such as precision geocoded and terrain

pg. 69 

geocoded will be available for FRS-1 & 2 and MRS mode data with user supplied GCPs’ information and available Digital Elevation Map information. Also for FRS-2 mode Polsar products will be available after proper validation.

(ii) Level-1 : Geo-Tagged Products (iii) Level-2 : Ellipsoidal Geocoded products Value added Products: �Precision Geocoded

7.4Image Quality Parameters: RISAT-1 products will nominally provided in CEOS format. This format will contain various products quality parameters like range resolution, ground resolution, azimuth resolution, peak side lobe ratio, integrated side lobe ratio, radiometric resolution, geometric error, resampling option, Datum used, relative phase error etc depending on the level of product. Also format will have information on processing related parameters such as no. of range and azimuth looks, azimuth bandwidth, range and azimuth weighting, Doppler centroid etc.

�Terrain Geocoded �Pol-SAR Products Fig.18 Strip map Imaging: FRS-1

The derivation of product code and the product code list are provided in Table-2& Table-3 Fig.19ScanSAR Imaging: MRS Definition of RISAT Data Products LEVELS (i) Level-0 :Raw signal products

TABLE.3 DPWFM RISAT-1 DATA PRODUCT CODES Code is 9 chars: PTMREELFM

SL.NO Description Typical

Values Meaning

1. Product Type ST Standard

Control Room

pg. 70 

PT

2. Map Projection M

0 P U

No Projection Polyconic UTM

6. Format C CEOS F T GeoTIFF

7. Media V DVD

3. Resampling R

0 C

No Resampling Cubic Convolution

M D DISK

4. Enhancement EE

00 No Enhancements

5. Correction Level L

0 Raw G** K N

Georeferenced (Terrain Corrected) ** Single Look Complex Slant range Multi Look Ground range

Note Please note that geo-referenced products are corrected for terrain heights.

TABLE.4 DPWFM PRODUCT

CODE LIST FOR RISAT-1 User Products 1) Level – 0 Raw Products

2) Level-1 Geotagged Products Single Look Complex (SLC) Products

Multi Look Ground Range Products

Product type Map Proj Resampling Enhancement Proc. Level Format Media

ST 0 0 0 0 C V/D

Product type Map Proj Resampling Enhancement P

ST 0 0 00 K

Product type Map Proj Resampling Enhancement P

ST 0 C 00 N

pg. 71 

3) Level-2 Terrain Corrected Products

8.Product Quality Control

Product Quality Control is responsible for checking the quality of all satellite data products that reach users. All RISAT-1 data products will be thoroughly verified and are subjected for stringent quality checks at PQC. Data products that conform to quality standards and specifications will be delivered to users. QC criteria for digital data products: All digital products will be verified as per thefollowing Checksheetthat comprises of different checks for products clearance. The main components of the checksheet are �Meta file verification �Format validation �Geometric check �Radiometric check through Visual inspection method �Band to Band Registration ( formultidate registered & merged products ) 8.1Meta file verification: A meta file is a .txt file that contains information about Satellite,Product and User. QC ensures the generation of a correct product from this file by crossverifyingthe information of user product with Data Products Work Flow Manager ( DPWFM ). QC verifies user specified parameters like Satellite, Mode ,Frequency, Incidence angle, date of pass, scene centre and corner coordinates , Projection, datum ,resampling and product code etc.

Product type Map Proj Resampling Enhancement Proc. Level Medium Media /Format /Size

ST U/P C 00 G C/T V /D

pg. 72 

8.2Format validation: RISAT-1 data products are supplied in CEOS and Geotiff formats. Data products are validated for correctness of format in auto mode at PQC through indeginous software. 8.3Geometric check :All digital products are checked for correctness of datum,mapprojection,resampling, resolution, scene centre, area coverage ( in terms of Lat./Long.) etc and should meet the user requirements ( in terms of corner co-ordinates and scene centre Lat./Long. ) and Location accuracy (as per mission ). 8.4Radiometric check :Radiomeric quality of data products is thoroughly verified for all products. . Different types of radiometric anomalies can be observed in data due to the complex nature of SAR data acquisition and processing. All RISAT-1 data products are subjected for data qualification through Visual quality assessment method. All digital products are displayed and viewed in full resolution mode with an option to zoom and roam in the image.Cent percent visual check is carried out to ensure good radiometric quality product. 8.5Band to Band Registration ( BBR ): BBR is a parameter that is to be verified for colour composite products . This is not an applicable parameter for RISAT-1 images since they are in black & white .But a colour composite product can be generated by registering different dates of SAR images or through merge process with optical data ( multi date registered product, merged etc). For such type of products , Band to band

registration check will be carried out byPQC .

pg. 73 

Products that meet QC standards will be delivered to users. Non conformal

products will undergo regeneration and re-certification.

pg. 74 

Flow chart of Digital products process Chain

RAC Computer

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9DATA ACCESS AND DISTRIBUTION

Introduction

Data products will be announced to the users after the initial phase validations by mission. User will be able to request for the data products either directly or through the User Order Processing System (UOPS). UOPS is an integrated web based application enables the user to register, browse and select the satellite images either from archives or plan for future collections, perform account related transactions, place orders and monitor the order status. Users, after browsing the images using the various queries and selecting the scenes, can place an order for the same using the ordering tools. Facility to obtain the status of user accounts and the orders placed is also available

online. Registered users can also change their details like address and their login password and send general queries through e-mail. ( Figure-15)

Upon connecting to the NRSC User order processing system site, the user is presented with a page with various links which enable the user to navigate through the application. If the user is new, he has to register himself for the ordering service to be enabled. While registering, the user has to agree to the terms and conditions displayed. A registration form is displayed in which he has to provide details like name, user identification (uid), password, user category, mailing address etc.,. Users

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have to remember their uid and password for future logins.

If the user is a registered user, he can sign in with his uid and password and enable the services.

UOPS opening page

Fig.20 Block diagram of User Order Processing System

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First page presented to the user. 9.1Services

Pre-requisites The services provided through UOPS are Browsing , ordering & future collections. If the user wants to just browse the data available in the archives browse should be clicked. If he wants to order the data he needs to click the order button then it will help him to browse as well as place order. If future collections are required then click on the collect button. Browsing / ordering services is a pre-requisite information provided to the users for converting the required area of interest into scenes and checking the data availability for the required area of interest. Before placing an order for data, the users need to browse through the data, to check for cloud and quality of the data. To meet this requirement, NRSC generates sub-sampled and compressed browse images along with

necessary ancillary information. This facility is made available to users through Internet. Compressed JPEG images are generated only for the Optical data sets for RISAT-1 no images are generated only the meta information is populated. This enables the user to verify coverage. The Browse facility has been integrated with data ordering and payload programming systems. Data can be browsed online and suitable scenes can be selected and converted into and data request by registered users who have an account with NDC. The different means of searching the image catalogue / ordering are : Either Map based search can be performed , which allows free draw on the world map or the options are AOI ,

Path and Date options. Under AOI based following options are provided.

• Shape file.

• Polygon Any one of these means can be selected as per the user convenience. • Mapsheet • Location

• Point Browsing / ordering services

9.1.1 Polygon based query/ordering/collects This option is useful to browse/order the images for a given geographical area. Users can input their area of interest either in terms of latitude/longitude in degrees, minutes, seconds or degrees decimal format of top left and bottom right corners or draw the area on a map with the help of mouse. On submitting the query, a form requesting the user to

enter the period of interest is displayed. On submitting, a list of scenes covering the user’s area of interest during the desired period shown to the right of the screen. On selecting the scenes and clicking on the layout option the scenes are plotted on the map. This enables the user to verify his area of coverage and also the number of scenes required. If the order button is clicked then the scenes selected can be ordered.

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Polygon based search

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The next screen presents the valid products based on the sensor , and allows various combinations of projections datum & resampling. The mode of dispatch also needs to be mentioned. If courier is opted then the products will be sent by courier if FTP is opted then the products will be uploaded on the web site for the users to download.

Once the cost estimate is shown Save PI Append PI and Generate Order are presented to the user. The user can Save the PI or Append into a already existing PI or directly generate order.

On clicking the estimate button it shows the cost estimate of the products.

Once the generate order button is clicked the complete PI is presented to the user along with accounts handled/allotted to the user. Then the user needs to select the account

through which the data cost has to be debited. Once the account number is selected. The Shipping address needs to be filled and confirm button to be clicked

.

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After the confirmation a pop-up window will be shown on the screen showing the Order No. This order number needs to be quoted for all future correspondences. After generation of products the status will be updated automatically. For the products through FTP mode , a mail will be sent to the user with the ip address and user name password. User can download the data using this.

Map sheet based products are one of the most popular products. So provision to query by map sheet number has been provided to facilitate easy querying by the user. In this case, apart from satellite, sensor, user has to select the map sheet number, either in open series map or as per the old SOI mapsheet numbers along with the period of interest. On submitting the query, a list of scenes covering the map sheet, during the desired period, are displayed. The user can then select the scenes and click layout option. This will plot the scenes on the map.

9.1.2 Map sheet number based Query

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9.1.3 Location name based query In case the user does not know anything other than the name of the location, he can use this query to browse the images covering the place during the desired period. The inputs to be provided by the user are satellite, sensor and the name of the place. Option

is available to use the data base of locations with “prefix” or “suffix” matching. The user is presented with the details of the scene covering his place and on what dates it was covered. The user can then, view the meta along with the plot on the map.

Location name based search

9.1.4. Point (Lat-Long) based query This query takes latitude and longitude of a single point and it maps to a square

based on the extent chosen. This query is useful if particular area around a point is to be viewed. User has to select the satellite, sensor, enter latitude and longitude of the point in degrees minutes seconds or degrees decimal

format and choose the extent of region desired. The extent of the region varies w.r.t. the sensor. On submitting, a list of scenes covering the extent with the

point as center, during the desired period, along with a graphical plot, is displayed. The user can then, view the meta along with the plot on the map.

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Point based search

9.1.5 Search for images based on shape file This query is useful for viewing the images dates when the input is in the form of a shape file generated in arcview format with geographic co-ordinates. The maximum number of points required in constructing the shape file should not exceed 10,000

.Users have to choose the satellite and sensor and submit along with the shape file in WGS 1984 Geographic /UTM projection format only. On submitting, a list of scenes covering the shape file are displayed. Provision for viewing the selected scenes plotted on the shape file is also provided. The users can then view the images and select.

Shape file based search 9.1.6Search for images based on date of pass /ordering When the date field is not entered at all, an alert message asking the date is displayed. However, a calendar is also provided along the date field for easy

operation. Based on the satellite relevant paths or orbits and sensor/modes are presented to the user. Users have to choose the satellite, sensor and the date of pass in dd-mm-

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yyyyformat . If a wrong value entered, an alert is displayed asking the correct

These scenes can then be ordered in the way explained in previous options.

This query is useful if the user wants to browse the images for a specific date. Date based search 9.2 ProductStatusMonitoring

Users can view the status of the request placed through the above options. This option gives the status as , dispatched , under production or alternate action .After viewing the status of the products, in case if any of the product

Order Processing and monitoring on Intranet by NDC

fails due to technical reasons, it can be re-generated by submitting a different date using the utility - Alternate date provided under pending actions.

9.3 Services for Offline Users: An off-line user is one who has one or more account numbers with NDC but has been placing orders for data by filling a paper order form. Order processing facility on Intranet enables NDC to monitor, distribute, process and dispatch the generated products to the customers placed offline.

10. Payload Programming

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10.1 INTRODUCTION RISAT is the first of the type with Synthetic Aperture Radar payload. Radar backscatter depends upon the sensor parameters such as frequency, polarization and incidence angle as well as on target parameters such as dielectric constant, roughness and geometry. The SAR on RISAT will operate in C band with both horizontal and vertical polarization. The SAR sensor is based on active phase array antenna technology and it provides electronic agility for achieving multimode imaging capability. So the imaging can be done both in ascending and descending passes of a day. The payload basically consists of an antenna 6mx2m in size consisting of 12X2 = 24 tile each tile having 24 X 24 radiating elements. The antenna is capable of generating 126 beams on either side of roll (i.e., +34 / -34). The payload is designed to operate in five different operation modes varying in swath and resolution. The swath and resolution are dictated by the usage of any set of beams out of 126 beams. (63 on each side) covering a very large of look angles. The beam width of the beams are so adjusted o provide a constant swath on ground irrespective of look angle.

Table.6 Mode wise Polarization

Table 1 & Table 2 gives the details of the modes an polarisations that are operable. Table.5 Imaging Modes

RISAT is a programable satellite. The data will be collected based on the

user specifications and as users need to give the look angle, period mode etc. Details of the inputs are discussed in the further sessions.Apart from data from arriving at the data collection needs NDC is also responsible in generating the final schedule files which is used by ISTRAC to further command the satellite. ISTRAC uploads the state vectors and other related files through the online facility which are further used for preparing the schedules. Total flow of action is described in the flow chart.

Flowchart of the programming activities

Various types of users are Handled by NDC as described below. 6.1 TYPES OF USERS: For programming 10.1.1 Registered Users: They are the registered users who can place programming requests for data acquisition. The users can place their programming request online through Internet . Once the inputs for collects are fed an online along with the product details ,proposal is displayed to the user. The proposal shows the dates on which the request can be serviced. Once the confirm button is clicked the dates are blocked for the user. After the data collection the status will be updated as serviced in the request status. Further the data

will be processed and dispatched to the user.

10.1.2 Offline Usres: The usres who do not have online accounts for placing request or still follow the conventional methods send us the request through fax or email. UOPS – INTRANET ( used by NDC scientists) has a provision for placing request offline. The proposals are sent to the usres and confirmation is saught for the user before planning. 10.1.3 Ground Station Users: Ground station users are the registered users who will acquire data in real time over their respective ground stations. These users are:

Nodal Ground station: They are responsible for the requests received from the ground stations handled by them. Ex. Space Imaging, Scanex. Individual Ground stations: These stations take care of the requests planned over their respective ground stations. Ex; TRN, DIP, DDN etc. Virtual Ground Stations: These are stations, which act as ground stations and they are governed by visibility circles. The data is collected by SSR and dumped at Svalbard or Shadnagar. 10.2 PAYLOAD PROGRAMMIGN ACTIVITY Payload programming activity involves programming the satellite acquisitions - based on the user requirements, International ground station requirements and for archival buildup. As RISAT provides different beam modes and the incidence angle or "beam positions”, this flexibility makes the

planning and ordering of RISAT data slightly more complex than that for other systems such as Resources at –I; This activity is split across three different systems located at NRSA and SCC. The UOPS is the front-end module, which accepts requests from users and International Ground stations online, through a web application. This system validates and transfers the requests to Swath planner. The Swath Planner is a tool, which calculates the predicted RISAT's orbit. It allows to generate, view, edit and analyse swath plans in order to identify the most suitable acquisition plan. Then a technical proposal is displayed to the user along with the graphical representation. After receiving the confirmation from user, PPS at NDC generates the schedules based on NDC selected options and sends it to SCC. At SCC the command sequence is generated for up-linking the satellite. The flow is described in the following flow chart.

10.2.1 Options for placing the programming request

5. High resolution spot light mode

Specify a range of beam positions an/or incidence angles

The different means of placing request for programming are Either Map based (free draw on the map) can be done or the options are AOI , Path and Date options. Under AOI based following options are provided.

Based on the modes acceptable beam positions will automatically be decided while planning. • Polygon CRS Mode – 12 Beams • Mapsheet MRS Mode – 6 beams • Location FRS Mode – • Point Or • Shape file. Minimum and Maximum Incidence angle should will be taken as input.

Location name – is treated as point request with specific radius around the point.

Or User application will be taken as input

Mapsheet:Can input Open series or the old SOI mapsheet numbers.

Period of Interest Inputs required form the user: Start Date

Specify pass direction End Date Polarization: Dual /circular 1. Ascending mode Priority: 2. Descending mode Urgent 3. Ascending and descending

mode Normal Emergency

Specify the imaging mode User can choose one of the priority options.

1. Coarse resolution mode

Normal: These requests can be placed 15 days in advance. These requests will not be charged for programming.

2. Medium resolution mode 3. Fine resolution striping

mode 4. Fine resolution strip map

mode Urgent: The requests, which are placed within T-2 days of

acquisition are treated as urgent. These will be included in the daily acquisition plan. These requests will be charged extra for acquisition. Ground stations send their stations request for a period of one week. The urgent request can be placed up to T-2 day

Confirmed: The requests which are confirmed for acquisition at SCC-PPS Serviced: The requests which are acquired on the specified day Cancelled: The requests which are cancelled by SCC due to various reasons

Closed: The requests which are successfully acquired (good quality,), will be updated as closed

Emergency: The user requests are of highest priorty followed by the archival build up. However in case of Natural calamities and man madeemergencies , all other requests take a lower priority. Requests placed in such cases with have high priority.

Repost: The requests for which the acquisition is not successful (bad quality) can be posted for another date. The status of such requests will be shown as Reposted. We need to have three such alternate dates for reposting. Only normal and urgent requests can have the reposting facility. Emergency requests for natural calamities will have only one acquisition.

10.2.2 REQUEST STATUS A request can have various statuses between posted and closed. The user will be able to view his request status online by keying in the request number. Various statuses are:

10.2.3 PPS - System

The Payload Programming system at NDC is designed as a multi mission Payload Programming system.

Posted: After the requests are finalized at SWATH PLANNER/UOPS they are posted at NDC-PPS. These requests show the status as posted.

It takes inputs from UOPS and allows for scheduling. Scheduled: The requests which

are accepted by NDC-PPS and sent to SCC-PPS

11.Applications

SAR is often used because of its all-weather, day or night capability, it also finds application because it renders a different view of a “target” with synthetic aperture radar being at a much lower electromagnetic frequency.Observations of the Earth using the SAR (Synthetic Aperture Radar) have a wide range of practical applications, such as: 11.1Forestry

BACKGROUND National Programmes as well as several corporates are investing

hugely on afforestation / plantation projects under Forestry / NREGS as well as social responsibility projects. In order to sustain them in long term, it is very important to monitor the progress of these planting efforts. Delineation of plantations in the forested area with optical RS data has several constraints. Use of high resolution SAR data has been very useful in the delineation of different type of plantations such as teak and associated species in deciduous forest areas.

INDIVIDUAL TREE CROWN DETECTION AND

FOREST OPENINGS

IDENTIFICATION OF Forest edges are generally marked by

remnant trees and clearances.

Individual trees are considered as key resources to sustainable livelihoods; contribute to above and below ground carbon stock and play a key role in the regulation of nutrient cycling. Forest clearances need to be

monitored for maintaining ecosystem quality. Hence, an all-weather observation tool is essential in tropical forest context. It can be realized with C-band high resolution remote sensing for this purpose. Fig.21 (A) RISAT-2- x-band VV data (B) FCC of variance (R),mean(G),Second moment (B) generated from GLCM matrix

Fig.22 (A)RISAT-2 X-band data (B) Cartosat-1 data showing individual tree crowns(C) FCC of IRS-P6 LISS-IV data and (D) RISAT-2 X-band data showing forest openings

11.2 Crop

One of major applications of SAR data is in the field of agriculture due to non-availability of cloud free optical data during the monsoon season and presently,

High resolution Spot mode Strip mode

Water

Scru

b la

nd

Urb

an

Water

Scru

b la

nd

Urb

an

Water

Scru

b la

nd

Urban

Water

Scru

b la

nd

Urban

Mango-new, Subabul, Trees, UnplowedPlowed fields, Mango-old,

SAR data is useful for delineating field boundaries, analysis of inter-field

variability and discrimination crops.

Fig.23Various Crop Fields

11.3 AGRICULTURE High resolution SAR data has potential application in the field of agriculture especially for generating field level information.

Fig.24 various agricultural

fields 11.4 Floods

Identification of flood inundated areas and estimation of flood damages are very crucial and difficult tasks to achieve during/after a flood wave. Flood mapping is one of the successful applications of SAR data in providing a synoptic view of the flood affected area due to its ability to penetrate through clouds. SAR data also helps in monitoring the flood situation at regular intervals of time.

ICRISAT Office

ICRISAT Office

R IS AT ‐2 

DL R ‐E S AR  C  

DL R ‐E S AR  X

DL R ‐E S AR  L  

Mango Urban WaterSubabul Trees Plowed land

To reduce the impact of flood disaster on human life and property, various flood control measures are implemented to protect the vulnerable areas. The major thrust was given for structural measures such as construction of embankments and spurs. Monitoring of these flood control structures are planned by flood control departments to identify the vulnerable river reaches after the flood recedes. High resolution SAR data helps in monitoring the vulnerability of these structures and plan for future flood control structures.

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