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NCAR-TN-16

Boundary Layer ProfileMeasurement System

C. P. EDWARDSE. Bollay Associates, Inc.Boulder, Colorado

March 1966

I UBIRRY

_ . .i_ .. ;: NCAR:! Technical Notes _____-NATIONAL CENTER FOR ATMOSPHERIC RESEARCH

Boulder, Colorado

; i NCAR Library

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The National Center for Atmospheric Research (NCAR) is dedicated to the advancement ofthe atmospheric sciences for the benefit of mankind. It is operated by the University Corpora-tion for Atmospheric Research (UCAR), a private, university-controlled, non-profit organization,and is sponsored an4.principally funded by the National Science Foundation.

NCAR shares with other atmospheric research groups four interrelated, long-range objectivesthat provide justification for major expenditures of public and private funds:

· To ascertain the feasibility of controlling weather and climate, to develop the tech-niques for control, and to bring about the beneficial application of this knowledge;

* To bring about improved description and prediction of astrophysical influences onthe atmosphere and the space environment of our planet;

· To bring about improved description and prediction of atmospheric processes andthe forecasting of weather and climate;

* To improve our understanding of the sources of air contamination and to bringabout the application of better practices of air conservation.

The research and facilities operations of NCAR are conducted in four organizational entities:The Laboratory of Atmospheric SciencesThe High Altitude ObservatoryThe Facilities DivisionThe Advanced Study Program

All visiting scientist programs and joint-use facilities of NCAR are available to scientists fromUCAR-member and non-member institutions (including private and government laboratories inthe U.S and abroad) on an equal basis. The member universities of UCAR are:

University of Alaska Florida State University Pennsylvania State UniversityUniversity of Arizona University of Hawaii Saint Louis UniversityUniversity of California The Johns Hopkins University Texas A and M UniversityUniversity of Chicago Massachusetts Institute of Technology University of TexasColorado State University University of Michigan University of UtahUniversity of Colorado University of Minnesota University of WashingtonCornell University New York University University of Wisconsin

NCAR-TN-16

Boundary Layer ProfileMeasurement System

C. P. EDWARDSE. Bollay Associates, Inc.Boulder, Colorado

March 1966

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NATIONAL CENTER FOR ATMOSPHERIC RESEARCHBoulder, Colorado

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iii

PREFACE

This report presents a brief survey of the capabilities of a new

tethered-balloon system for making meteorological measurements of the

boundary layer profile up to 5000 ft above the ground. The airfoil

balloon is designed to maintain altitude in the face of winds at flight

altitude.. The system was developed by E. Bollay Associates, Inc.,

Boulder, Colorado, under subcontract to NCAR. The author is a staff

member of E. Bollay Associates, Inc.

The system is available to meteorologists at other institutions

for cooperative research use. Detailed information can be obtained from

the Field Observing Facility of the National Center for Atmospheric

Research, Boulder, Colorado.

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BOUNDARY LAYER PROFILE MEASUREMENT SYSTEM

The NCAR Field Observing Facility has developed a tethered-balloon

wing system to accurately measure the vertical profile of temperature,

wind speed, wind direction, and humidity. Readings can be made up to

5000 ft above the ground (for ground elevations up to at least 5000 ft

ASL).

The system consists of a Mylar balloon wing, a 2-lb telemetry

package, an electrically operated winch, and a ground receiver with

magnetic tape recorder.

The balloon wing (Fig. 1) contains approximately 112 cu ft of

helium and is designed so that it does not require FAA waivers to FAR,

Part 101. It is not difficult to launch and is rigged in a unique

Fig. 1--Balloon wing.

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fashion, so that lift due to strong winds is kept at a safe level. The

balloon is durable and can be operated in temperature extremes without

rupture. A normal round trip to 5000 ft above terrain and return re-

quires 30 min.

The telemetry package (Fig. 2) contains the various transducers, a

403 MHz transmitter, and an 8-hr rechargeable battery supply. Temperature

is sensed by a precision thermistor, humidity by a semiconductor element

("Hygropack"), wind speed by a low-threshold 3-cup anemometer, and wind

direction by a magnetic compass which establishes an azimuth reference

for the balloon wing. The height of the vehicle is measured by a pres-

sure altimeter. The outputs from all of these transducers are converted

into dc voltage analogs. These dc voltages are selected in time se-

quence by a solid state commutator. The output of the commutator is tele-

metered by converting it to an analog audio frequency which in turn

frequency modulates the 403 MHz transmitter. The commutator generates

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a standard IRIG word frame that includes a full-scale synch pulse. The

commutation rate can be varied to suit the response times required and

the type of data recovery equipment. The format of the commutator is

compatible with standard decommutation equipment; however, it can also

be manually recovered with a standard strip chart recorder.

The winch is operated from 24 vdc and is mounted on a 4-wheel

trailer (Fig. 3). Sufficient room is available on the trailer for the

Fig. 3--Trailer-mounted ground station. Receiver complexon left, helical antenna on right, balloon handlingboom and winch in center.

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ground receiver and recorder. Limit switches automatically control the

tether line tension. The ground station mounted on the trailer uses a

helical receiving antenna and a standard FMQ radiosonde receiver.

An Ampex 1100 series tape recorder records the audio output of the

receiver. The final recovery of the dc analog voltages from the re-

corded audio tones is done by a standard IRIG discriminator. Figure 4

shows the receiver, discriminator, and tape recorder.

Fig. 4--Close-up of receiver, discriminator, and tape recorder.

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Big. 4-Close-u of reciver, dscrimint.. ............. der

SPECIFICATIONS

SPEC IF ICATIONS

6:

SPECIFICATIONS

BALLOON WING

Volume 112 ft3

Lift 4 lb net

Material 1/4 mil Mylar bilaminatewith nylon scrim

Helium for fill plus one week operation 1 bottle (-220 ft )

Angle from verticalat 20 m/s wind 20 'maximum

TELEMETRY PACKAGE

Measurements

Temperature -15 to +35°C, ±0.2°C

Humidity 10 to 95%, ±2.5%

Wind speed >0.1 to 20 m/s, ±0.5 m/s

Wind direction 0 to 360°, ±10°

Height 0 to 1500 m, ±10 m

Spare channels 2 channels requiring 0 to 100 mvat >10 K ohms source impedance

Modulation

Type PAM-FM (time multiplex)

Frequency IRIG channel #8 (3 kc ±7.5%)

Format 3-channel width full-scalesynch pulse plus 7 informationchannels with 50% duty cycle

Commutation rate Variable, 0.5 to 50 channels/sec

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TELEMETRY PACKAGE (cont'd)

Transmitter

Frequency 403 MHz nominal

Modulation index 5 (at 3 kc)

Power 50 mw

Antenna Crossed dipole with seconddipole feed 90° late to producecircular polarization

Power 9.6 volts 0.250 A/h and 12 volts0.500 A/h nickel cadmium batteries

Construction

Size 4 in. dia x 11 in. long

Weight 2 lb 5 oz

GROUND STATION

Receiver R-228/FMQ-2(390 to 410 MHz)

Recorder Ampex model 1160(operating at 1-7/8 in./sec)

Antenna Mark Products CompanyH-450 helix

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