SOLRAD 10

Solrad 10

Solrad 10.
Mission type	Heliophysics
Operator	NASA
COSPAR ID	1971-058A
SATCATno.	5317
Spacecraft properties
Manufacturer	Naval Research Laboratory
Launch mass	260 kilograms (570 lb)
Start of mission
Launch date	July 8, 1971, 22:58(1971-07-08UTC22:58Z)UTC
Rocket	Scout BS177C
Launch site	WallopsLA-3A
End of mission
Decay date	15 December 1979(1979-12-16)
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Eccentricity	0.0006626
Perigee altitude	204 kilometers (127 mi)
Apogee altitude	213 kilometers (132 mi)
Inclination	51.0598°
RAAN	328.0487°
Argument of perigee	235.3867°
Mean anomaly	124.4027°
Mean motion	16.23884333
Epoch	13 December 1979
Revolutionno.	46942
Explorers Solrad

Solrad 10,also knownExplorer 44,NRL-PL 165andExplorer SE-C,was one of the SOLRAD series designed to provide continuous coverage ofwavelengthand intensity changes insolar radiationin theUV,soft and hardX-rayregions. The satellite also mapped thecelestial sphereusing a high-sensitivity X-ray detector.Information collected was expected to contribute to a better understanding of the physical processes involved in solar flares and other solar activity, and the potential effects of this activity on short-wave communications, as well as on future human space travel.For the period of July 1971 to June 1973, the core memory data of Explorer 44 (SOLRAD 10) were used rather than those from Explorer 37 (SOLRAD 9). The Explorer 44 (SOLRAD 10) core memory failed on 11 June 1973, and Explorer 37 (SOLRAD 9) was heavily used until 25 February 1974, when the gas supply of theattitude control systemwas exhausted.

Launch

Solrad 10 was launched on 8 July 1971 fromWallops Flight Facility,Virginia,with aScout rocket.When it was launched, it had an orbit with 630 kilometres (390 mi) ofapogee,436 kilometres (271 mi) ofperigee,51.1 degrees oforbital inclinationand 1 hour and 35 minutes oforbital period.

It launched fromWallops Island,Virginia,into a 436 × 630 km (271 × 391 mi) orbit. The plane of rotation shifted about 1°/day so that a stellar detector mounted to point radially outward from the axis scanned the celestial sphere. Data from all detectors were stored in a 54-kbs core memory and telemetered on command to theUnited States Naval Research Laboratory(NRL) tracking station at Blossom Point,Maryland.Data were also transmitted in real time at 137.71-MHz and were shared with the international scientific community throughCommittee on Space Research(COSPAR). Expected lifetime was 3 years.

Spacecraft

Solrad 10 was a 12-sided cylinder that measured 76 centimetres (30 in) in diameter and 58 centimetres (23 in) in height. Four symmetrically placed 17.8 by 53.3 centimetres (7.0 in × 21.0 in)solar cellpanels, hinged at the central section of the structure, served as the elements of a turnstileantennasystem. 18 solar sensors were mounted pointing parallel to the spin axis of the satellite, which pointed directly at the solar disk. The plane of rotation shifted about 1°/day so that astellardetector mounted to point radially outward from the axis scanned the celestial sphere. Data from all detectors were stored in a 54kbcore memoryand telemetered on command to theNRL Satellite Operations CenteratBlossom Point, Maryland.Data were also transmitted in real time at 137.710MHz.

Experiment

All-Sky X-Ray Survey

This experiment was designed to map the sources of X-ray emission in the sky in the 0.5 - 15-A region. The detector, mounted on the side of the spacecraft, was a large-area proportional counter mounted to point radially outward from the spin axis, which pointed continually toward the sun. The detector window was made of 1/8-mil-thick mylar with an effective area of 100-cm².The gas filler was a mixture of 0.45argon,0.45xenon,and 0.10carbon dioxidemaintained at 4 lb/cm².A collimator limited the field of view to 8°, full width at half maximum (FWHM) in a plane containing the spin axis and 1° in the plane perpendicular to the spin axis. Charged particle information was provided by proportional counters mounted on three sides of the X-ray detector. Aspect information was provided by a blue-sensitive photomultiplier capable of detecting allfourth-magnitudeand not fifth-magnitude stars. The resolution of the aspect system and the accuracy with which the experiment could locate X-ray sources was better than ± 0.25°. The detector was connected to a 400-channel pulse time analyzer which was synchronized with the spin period to give a 2° spatial resolution in the spin direction. The wholecelestial spherewas surveyed every 6 months. Due to the low altitude of the satellite, there was a high charged-particle count at all times. This background limited the usefulness of the data, and no results from this experiment were published.

Solar Radiation Detectors

This experiment was designed to monitor the solar X-ray flux in eight bands and the solar UV flux in five bands as part of a long-term project to observe solar X-ray and UV activity with sets of standardized sensors over anentire solar cycle.The X-ray bands observed were 0.08 to 0.8 A, 0.1 to 1.6 A, 0.5 to 3 A, 1 to 5 A, 1 to 8 A, 8 to 16 A, 1 to 20 A, and 44 to 60 A. All the detectors for these bands, with the exception of that for the 0.08- to 0.8-A band, wereionization chambersfitted with a variety of window material (beryllium,aluminum,andMylar) of various thicknesses and filled with several different gases (krypton,argon,nitrogen,Carbon tetrachloride,andxenon) at various pressures. The 0.08- to 0.8-A band had as a detector a cesium iodide(CSI) (Na) scintillating crystal surrounded by aplasticscintillating material viewed by a singlephotomultiplier.This detector was designed to collect data on the very high-energy solar X-ray emission observed only during solar flares. TheUVbands observed were 170 to 500 A, 170 to 700 A, 1080 to 1350 A, 1225 to 1350 A, and 1450 to 1600 A. The two shorter wavelength bands hadlithium fluoride,photosensitive surfaces protected by aluminum,aluminum oxide,andcarbonwindows for detectors, while the remaining bands had ion chambers with windows composed of lithium fluoride,calcium fluoride,orsilicon dioxide,and various gas filters (nitric oxideortriethylamine 8). Some of the solar detectors were protected from charged particles by cone-shaped aluminumcollimators.The data were transmitted over two telemetry systems in one of three forms—stored data, real-time digital (PCM) data, and real-time analog data. Telemetry system 1 (TM 1) used a PAM/PCM/FM/PM transmitter that operated at 137.710 MHz with a radiated power of 250 MW. Under normal operating conditions, TM 1 continuously transmitted analog and PCM real-time data, although the real-time digital PCM was the primary real-time transmission format. Telemetry system 2 (TM 2) used a PCM/PM transmitter that operated at 136.38-MHz with a radiated power of 250MW.TM 2 transmitted stored data (up to one data sample a minute for 14.25 hours) on command.

Atmospheric entry

Explorer 44 (SOLRAD 10) returned to theatmosphere,disintegratingon 15 December 1980,or December 15, 1979.

See also

• Solrad 9

External links

• SOLRAD/GRABArchived2018-06-20 at theWayback Machine.Naval Research Laboratory