The Solar Maximum Missionsatellite (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 as well as the Upper Atmosphere Research Satellite.
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 onboard 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.
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, maneuvering it into the shuttle's payload bay for maintenance and repairs. SMM had been fitted with a shuttle "grapple fixture" so that the shuttle's robot arm could grab it for repair. 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. The mission was depicted in the 1985 IMAX movie The Dream Is Alive.
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.
^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.
^"STS-41-C Press Kit". 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.
^"STS-41-C Press Kit". 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.
Payloads are separated by bullets ( · ), launches by pipes ( | ). Manned flights are indicated in bold text. Uncatalogued launch failures are listed in italics. Payloads deployed from other spacecraft are denoted in (brackets).