magnetic field measurements by pioneer 7 norman …
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X-690-71-4522-:EPRIN?
MAGNETIC FIELD MEASUREMENTS,BY PIONEER 7
I. Hourly Average. . \ .,.~~~~~~~
Elements from- 17to 29 October 1967
'RotationI
s of the Field-August 1966' (Bartels' Solar
1820 to 1836),
GODDARD SPACE ,FLIGHT CENTER "GREENBELT, MARYLAND , .
N N72- $2 3 3
Uncl as09756
7 (NAS A-TM-X-65169) HAGNETIC FIELDMEASUREMENTS BY PIONEER 7. 1: HOURLYAVERAGES OF THE FIELD ELEMENTS FROMI17 AUGUST 196 TO 29 N.F. NeSS, et al
(NASA) Nov. 1971 42 p S
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X-690o-71- 452
MAGNETIC FIELD MEASUREMENTS BY PIONEER 7
I. Hourly averages of the field elements from 17 August1966 to 29 October 1967 (Bartels' Solar Rotation 1820to 1836)
Norman F. NessFranklin W. Ottens
Laboratory for Extraterrestrial PhysicsNASA-Goddard Space Flight Center
Greenbelt, Maryland USA 20771
November 1971
1. Introduction
The Pioneer 7 spacecraft is a spin stabilized interplanetary
probe launched from the Eastern Test Range, Cape Kennedy, Florida on
17 August-196 6 . The geocentric orbit of the spacecraft has an aphelion
of 1.125 AU, a perihelion 1.010 AU, inclination to the ecliptic of 00
and orbital period of 403 days. This spacecraft was the first of a
series of four Pioneer spacecraft with identical structures but slightly
different complements of experiments. A NASA-GSFC magnetic field
experiment was proposed, accepted and flown on Pioneers 6 (in 1965)--and 7.
Subsequently, unique circumstances presented an opportunity for flight
of a similar experiment by the GSFC group in collaboration with the
University of Rome, Laboratory for Space Plasma Research group on
Pioneer 8 (in 1967).
The magnetic field experiment detector is a monoaxial fluxgate
magnetometer sensor mounted on the end of a boom at a distance of 2.1
meters from the spacecraft spin axis. The initial spin period was
approximately one second and the field measurements were synchronized
with the rotation of the spacecraft. The monoaxial sensor was oriented
at an angle of 540 45' to the spin axis so that during one spacecraft
rotation three samples of the magnetic field at equal intervals yielded
three independent measurements in mutually orthogonal directions. These
basic measurements, obtained in a time interval of 2/3 of a second,
define the total vector magnetic field in a spacecraft coordinate system.
-2 -
The spin axis of the spacecraft was oriented orthogonal to the ecliptic
plane with the high gain antenna of the spacecraft pointing to the south
ecliptic pole.
Data transmission from the spacecraft experiment was synchronized
with telemetry, which ranged from 8 to 512 bits/sec during the lifetime
of the spacecraft. A complete three component measurement was not read
out during each spin period and so individual data points are not
equally spaced in time (see Scearce et al., 1968 for description of
the experiment).
The Pioneer 7 instrument was a single range magnetometer (+32r)
which with the 8 bit quantization of the analog to digital converter
yielded a digital window size of +O.125y. The RMS noise level of the
sensor was 0.12y and the bandwidth 0 to 5 cps. The magnetic field of
the spacecraft and associated solar array as measured at the sensor
location was estimated to be less than 0.6y. Periodic sensitivity
calibrations were made once each day as well as zero level checks
approximately once every several months. The projection of the orbit
described by Pioneer 7 on the ecliptic plane, relative to the earth-
sun-line, is shown in F-i-gure 1.
-3-
2. Data
The magnetic field elements have been computed in a spacecraft
centered solar ecliptic system in which the X axis points from the
spacecraft to the sun, the Z axis to the ecliptic north pole and the-
Y axis being the third axis of the orthogonal right handed coordinate
system.
The standard data analysis was performed to yield 30 second averages
of the field components and the field magnitudes as
n n-1 XtFn 1Fi, F =Nf`xL+(Y)2+(Z(1)
Xi etc., F =/))+ (1)i=l i=l
Also RMS deviations ( X' By, 8Z) of the magnetic field were computed
routinely for each component and for the field magnitude. The Pythagorean
variance, which is an invarient of the coordinate system, is obtained
from the component deviations as
2 2 2
6= i8x + By +8 z(2)
The choice of a 30 second time interval was based upon a desire
to provide correlative data to each of the plasma probes on the Pioneer
6 and 7 spacecraft whose fastest cycle times were on the order of one
minute.
Data shown in Figures 2 through 17 represent for each solar rotation
the hourly averages of the field elements F, F, 0 (latitude) and 0 (longitude).
The data are plotted in 27 day increments corresponding to Bartels' solar
-4-
rotation numbering system. The two variances D1 and D2 are obtained by
different means. D1 is a variance computed from equation 2 for each
hourly interval using the hourly averaged components (and deviations from
them). D2 is the hourly average of the individual Pythagorean variance
for each 30 time interval. The days of the year are indicated as calendar
days and most of the missing data corresponds to gaps in tracking
coverage of the spacecraft. Publications utilizing Pioneer 7 data which
have already appeared are given in the reference list. This does not
include those publications by other non-GSFC associated authors who have
used Pioneer 7 data.
-5-
3. Summary
The orbit of Pioneer 7 was such that for much of its early
lifetime (several months) it was located in the aftward portion of
the disturbed solar plasma caused by interaction with the geomagnetic
field. Observations of the geomagnetic tail at the greatest distance yet
achieved (100O RE) were performed by this experiment. (Nest et al.,
1967; Fairfield, 1968). Important simultaneous correlated measurements
of the electron component of the plasma in the neutral sheet and the
associated magnetic field were first performed by Pioneer 7 (Lazarus et
al, 1968).The 30 second average detail data and hourly average data are
available from the National Space Science Data Center at NASA-GSFC
(Mail Code 601), Greenbelt, Maryland 20771. This present document
provides, in summary graphical form, a working data set which was used
internally at the NASA-GSFC and parts of which have been made
available to other groups.
-6-
4. References -(in chronological order)
1. Ness, N. F., C. S. Scearce and S. C. Cantarano, Probable Observation
of the Geomagnetic Tail at 103 RE by Pioneer 7, J. Geophys. Res., 73,
3769-3776, 1967. (Also X-612-67-183).
2. Lazarus, A. J., G. L. Siscoe and N. F. Ness, Plasma and Magnetic
Field Observations During the Magnetosphere Passage of Pioneer 7,
J. Geophys. Res., 73, 2399-2409, 1968.
3. Fairfield, Donald H., Simultaneous Measurements on Three Satellites
and the Observation of the Geomagnetic Tail at 1000 RE, J. Geophys.
Res., 73, 6179-6187, 1968.
4. Ness, Norman F., The Geomagnetic Tail, Revs. Geophysics, 7, 97-128,
1969, (Also X-616-68-345).
5. Scearce C. S., C. Ehrmann, S. C. Cantarano and N. F. Ness, Magnetic
Field Experiment: Pioneers 6, 7 and 8, X-616-68-370.
6. Ness, Norman F., The Magnetic Structure of Interplanetary Space,
Proceedings Budapest XI International Cosmic Ray Conference,
(Also X-6X6-69-334.)
7. Mariani, F., B. Bavassano and N. F. Ness, Magnetic Field Fluctuations
in the Magnetosheath Observed by Pioneer 7 and 8, J. Geophys. Res., 75
6037-6049, 1970 (Also X-616-69-541).
List of Figures
1 Projection of the orbit of Pioneer 7 on the ecliptic plane. Positionof the spacecraft for the first day of each month is indicated bymonth/year.
2- Hourly averages of the magnetic field elements F, Fs, , 0, D1 and18 D2 for the Bartels' solar rotation number specified on the left
hand side. The lack of two values for F, F, means that thespacecraft was in the DCS (Duty Cycle Storage) mode of operationwith delayed transmission of data. The character A representsthe "folding over" of the corresponding scale by the maximum valueof the scale as shown on the left, Hence the correct value is tobe read = A + Max Scale. Gaps in data are due to lack of telemetryrecording by NASA-JPL DSN stations.
I SUN 1.0
EARTH 10/66
12/66
PIONEER 7 7._.
2/67
10/67 4/678/67
6/6712/67 30o
VFIGiRE 1
4.
D2 1 _rsuJJfnvL
DI 8.1
0.
C\j 270. '
180.
.- -
F 12.
6.
230 231 232 233 234 235
0.1 7 21 24
AUG. 1966FIGURE 2
, @OUT FRAME 2
D2
N0
Z
m
-J0uW
4.
0.16.
DI 8.
0.360.
270.
I so180.
90.
0.90.
-90.
24.
18
FF 12.
6.w
O. L24 28 30
AUG. 1966 SEPT. 1966
I AN1A Vt I I
164 8 I : 20
FIGURE 3
.OlpOUT FRAME2
_R
I
I-
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FOLDOUT FRAME I E.LDOUT FRAME 2
D2
DI
4.
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8.
0.
360.
270.
180
90.
O.90.
-90.24.
18.
12.
6.
0.20 I
SEPT. 196624 28 5
OCT. 1966
FIGURE 4
12 16
CM
z0
0Or
0n, F
F
T Sr1277
rAd·i~
qr IV·
EQLDOUT FRAME (
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DI
ro)
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8.
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90.
0.90.
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24.
la
12.
6.
0.
IIV N Am
17
OCT. 196622
Ip26 30
NOV. 1966
FIGURE 5
'QIDOUT FRAME 2
A
9
310' Iso 13oI 13o6 oe1304 1305 1306 1 1308
12
FOLDOUT FRAME2FOLDOUT FRAMDI
3 36 1337 1331
17 21 25 30 1
NOV. 196695
1966
FIGURE 6
D2
DI
q_.C0
z0
It
n FF
4.
0.16.
8.
0.360.
270.
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90.
O.90.
24.
18.
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0.
�Pky�
13
FOLDOUT FRAMEJ
4
16 t
0 I f I
12
6
20 24 28
DEC. 1966
FOLDOUT FRAME2
30
I 12 3 14
1 JAN.2 3 4 5JAN. 1967
FIGU1:E 7
D2
DI
360
270
180
90
090
e
18
L)c\jco
z0I-H
0
0-
0(I)
13 ll
fI
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4
I Q4
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24
JAN. 1967
FIGURE 8
FOLDOUT FRAME2
27
D2
DI
(0c'C)
,8
8
36°0
270
180ISO
90
98
8
0
Z
I
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18
12
6
30
FEB. 1967
ld ,TA
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FOLDOUT FRAME d
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8.
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if
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FIGURE 9
FOLDOUT FRAME 2
27
D2
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z0
I-
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O
°nFF
2FEB. 1967
_ _ _ _ _ __ ._ ~_ _ _ _ _ ._ _
22
FOLDOUT FRAME 2OPLDOUT FRAME l
D2
DI
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Z0
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0
n-
n-0O3 F
F
4.
0.16.
8.
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90.
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18.
12.
6.
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MAR. 1967
FIGURE 10
A
24
86
27
OLDOUT FRAME I
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13:
<:1
F
4.
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18.
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6.
o.
I
28
MAR. 19675 9
APRIL 1967
FIGURE 11
FOLDOUT FRAME 2
107 _ 108 Io 1
17 21 24
FOLDOUT FRAMP i OUt FRAM_
PIONEER HOURLT AVERRGES
D2 o. U I
D(~~~~~~~~~~~~ ~~~~~~~~ Is_~ ]l 1~ ii l
16j.
0 o. ______ _ __ i I I L I i _ Io 360.r'-o270.
o 90.115 116 117 o 119 i 120 121 122 123 124 125 126 127 128 t129 130 131 132 33 134 138 139 140
0. 90.
6.
n,' -eo. I I I I I I I I I I I I I I4 8 2I24.
n,"
1 12. 118 8
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FIGURE 12
FOLDOUT FRAME Z
PIONEER HOURL" VEARGE'
-F( li L -L iI I II I
-""7r~ls ~ I [ _ I LI I [ I I I I I I
156~ ~ ~ 15 5 5 6 6 6 16 164 161
'_ I~~~~~ t'
I]I I I I I I I I I i f
j
142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 58 _59
_ I I . - .___ _ I I ._. ff I I _ , . ._ I- - _ _ _
25 29 5
JUNE 1967
FIGURE 13
160 161 162 163 164 16 166 167-_. _ I _ I
13
r16
D24.
0.16.
DI 8.
0.360.
270.
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90.
0.90.
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Co
0z0
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18. -
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O.21
MAY 1967
FQOLDOU-T- Fi^M9
FOLDOUT FRAME IFOLDOUT FRAME 2
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270.
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90. 6
0o.90.
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18.
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6. i .m -
0.172 173 174 175 176 177 178 179 180 181 182 183 184 185 186
21 25 29 I 5
JULY 1967
FIGURE 14
I I
/
8 18_ 9 190 191 192 193 1948 12___I 1
CMP()
z
0-e
I-
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17JUNE
JUNE 1967
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O 90.
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. 18.On F
F 12.
6.
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PIONEER HOURLY RVERRGES
A I . I I I_ , -I
4 - t JV
iI I I I I I I I I I I I I
4
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1
I I I I I I I I I J I I I
196 197 198 199 1200 201 202 203 2I II _ _f 120i 209 1210 211 212 1213
14
JULY 196718 22 26 30
AUG
FIGURE 15,
FOLDOUT FRAME'
I I I I I I I
14 215 216 217 218 219 220 221_ _- 1 1_.1 .__
14 215 216 217 218 219 220 221I I- 1 _.-I__
5 9
1967
..... ~~ & I I I I & I
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(On FF
4.
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90.
0.90.
-90.24.
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6.
0.
Marv jf
14 22 2710 18
AUG. 1967
FIGURE 16
FO~DOUT FRAME'Z
rl
jq I243 244 245 246 247 248
1 -r I - ffI - -
i
243 244 5 246 1247
31 1 4
SEPT. 1967
inl
I 1 I I I I
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r A
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SEPT. 1967
FIGURE 17
wi nnllT FRAME Z
.i I I I __--
j269 270 -- 271
27
'I 72 2 73 274 275If I LL
OCT. 1967
l
FOLDOUT. FRAM;E I
As
14 1285 286 287 288 289 1290 1291 292 4293 91 12 ___f ____f _3 f
9 14 20
FIGURE 18
LIpOUT FRAME 2
I . ., L I . I I L
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297 298 299 300 301 302I .. i_ ~__r I__ 0
25 29
D2
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OCT. 1967
I I I -- Iv~
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