Solar Maximum Mission

Solar Maximum Mission

Mission type	Solar physics
Operator	NASA
COSPAR ID	1980-014A
SATCAT №	11703
Mission duration	9 years
Spacecraft properties
Bus	Multimission Modular Spacecraft
Manufacturer	Fairchild Industries
Launch mass	2,315.0 kilograms (5,103.7 lb)
Dimensions	~4 by 2.3 metres (13.1 by 7.5 ft)
Start of mission
Launch date	February 14, 1980, 15:57:00 UTC
Rocket	Delta 3910
Launch site	Cape Canaveral Air Force Station LC-17A
End of mission
Decay date	December 2, 1989
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Eccentricity	0.00029
Perigee	508.0 kilometers (315.7 mi)
Apogee	512.0 kilometers (318.1 mi)
Inclination	28.5 degrees
Period	94.80 minutes
Mean motion	15.19

Astronaut George Nelson attempts to capture the Solar Maximum Mission satellite during STS-41-C

The Solar Maximum Mission satellite (or SolarMax) was designed to investigate Solar phenomena, particularly solar flares. It was launched on February 14, 1980. The SMM was the first satellite based on the Multimission Modular Spacecraft bus manufactured by Fairchild Industries, a platform which was later used for Landsats 4 and 5^[1] as well as the Upper Atmosphere Research Satellite.

The Solar Maximum Mission ended on December 2, 1989, when the spacecraft re-entered the atmosphere and burned up.

Instruments

Experiments on board the Solar Maximum Mission

Name	Target	Principal Investigator
Coronagraph/Polarimeter: 446.5-658.3 nm, 1.5- 6 sq.solar radii fov, 6.4 arcsec res.	Solar corona, prominences, and flares	MacQueen, Robert M., High Altitude Observatory
Ultraviolet Spectrometer and polarimeter 175.0-360.0 nm raster imager, 0.004 nm sp.res.	Solar UV, Earth's atmosphere	Tandberg-Hanssen, Einar A., NASA Marshall Space Flight Center
Soft X-ray Polychromator: raster imager, crystal spectrom. in parts of 0.14-2.25 nm	Solar flares, active solar regions	Acton, Loren W., Lockheed Palo Alto, Culhane, J University College, London, Leonard, Gabriel, Alan-Henri, Rutherford Appleton Laboratory
Hard X-ray Imaging Spectrometer: fov 6.4 arcmin, 8 or 32 arcsec res, 3.5-30 keV	Solar active regions and flares	de Jager, Cornelis, University of Utrecht
Hard X-ray Burst Spectrometer: CsI(Na), 15 energy channels covering 20-260 keV	Solar flares and active regions	Frost, Kenneth J., NASA Goddard Space Flight Center
Gamma-ray Spectrometer: NaI(T1),0.01-100 MeV in 476 channels, 16.4 s per spectrum	solar gamma-rays	Chupp, Edward L, University of New Hampshire
Active Cavity Radiometer Irradiance Monitor: 0.001-1000 micrometer solar flux	solar irradiance	Willson, Richard C, NASA Jet Propulsion Laboratory

Failure and repair

In November 1980, the second of four fuses in SMM's attitude control system failed, causing it to rely on its magnetorquers in order to maintain attitude. In this mode, only three of the seven instruments on board were usable, as the others required the satellite to be accurately pointed at the Sun. The use of the satellite's magnetorquers prevented the satellite from being used in a stable position and caused it to "wobble" around its nominally sun-pointed attitude.^[2]

The first orbiting, unmanned satellite to be repaired in space, SMM was notable in that its useful life compared with similar spacecraft was significantly increased by the direct intervention of a manned space mission. During STS-41-C in 1984, the Space Shuttle Challenger rendezvoused with the SMM, astronauts James van Hoften and George Nelson attempted to use the Manned Maneuvering Unit to capture the satellite and to bring it into the orbiter's payload bay for repairs and servicing. The plan was to use an astronaut-piloted Maneuvering Unit to grapple the satellite with the Trunion Pin Attachment Device (TPAD) mounted between the hand controllers of the Maneuvering Unit, null its rotation rates, and allow the Shuttle to bring it into the Shuttle's payload bay for stowage. Three attempts to grapple the satellite using the TPAD failed. The TPAD jaws could not lock onto Solar Max because of an obstructing grommet on the satellite not included in the blueprints for the satellite. This led to an improvised plan which nearly ended the satellite's mission. The improvisation had the astronaut use his hands to grab hold of a solar array and null the rotation by a push from the Maneuvering Unit's thrusters. Instead, this attempt induced higher rates and in multiple axes; the satellite was tumbling out of control and quickly losing battery life. SMM Operations Control Center engineers shut down all non-essential satellite subsystems and with a bit of luck were able to recover the satellite minutes before total failure. The ground support engineers then stabilized the satellite and nulled its rotation rates for capture with the Shuttle's robotic arm. This proved to be a much better plan. The satellite had been fitted with one of the arm's "grapple fixtures" so that the robotic arm was able to capture and maneuver it into the shuttle's payload bay for repairs. During the mission, the SMM's entire attitude control system module and the electronics module for the coronagraph/polarimeter instrument were replaced, and a gas cover was installed over the X-ray polychromator.^[3]Their successful work added five more years to the lifespan of the satellite. The mission was depicted in the 1985 IMAX movie The Dream Is Alive.

Findings

A coronal transient as seen by the SMM on May 5, 1980

Significantly, the SMM's ACRIM instrument package showed that contrary to expectations, the Sun is actually brighter during the sunspot cycle maximum (when the greatest number of dark 'sunspots' appear). This is because sunspots are surrounded by bright features called faculae, which more than cancel the darkening effect of the sunspot.

The major scientific findings from the SMM are presented in several review articles in a monograph.^[4]

The SMM discovered ten sungrazing comets between 1987 and 1989.^[5]

See also

• Solar and Heliospheric Observatory
• WIND (spacecraft)
• Advanced Composition Explorer
• Solar Probe Plus
• Charles Hyder

References

1. Suzuki, Masaharu (11 February 1999). "TOPEX/Poseidon - Description of Mission". University of Texas. Retrieved 9 July 2013. The satellite bus was taken from the Multimission Modular Spacecraft (MMS), which has been proven on previous MMS-based missions: the Solar Maximum Mission and Landsat 4 and 5.
2. "STS-41-C Press Kit" (PDF). NASA. Retrieved 9 July 2013. All four of those instruments require pointing accuracy from the spacecraft and could not function effectively with the spacecraft spinning through space with its longitudinal axis pointed toward the sun, as it has since the attitude control system failure.
3. "STS-41-C Press Kit" (PDF). NASA. Retrieved 9 July 2013. Repairs to be made during the mission include replacing the attitude control system module, replacing the main electronics box on the Polarimeter/Polarimeter, and placing a cover over the gas vent of the X-Ray Polychrometer.
4. Strong KT; Saba JLR; Haisch BM; Schmelz JT, eds. (1999). The many faces of the sun : a summary of the results from NASA's Solar Maximum Mission. New York: Springer. Bibcode:1999mfs..conf.....S.
5. "JPL comet catalogue".

External links

• HEASARC, SMM
• Marshall Space Flight Center, SMM
• SMM C/P Coronal Mass Ejections
• Total Solar Irradiance ACRIM