SMM (Solarmax)

SMM [NASA]

NASA's SMM (Solar Maximum Mission) or SolarMax was a solar observatory built by Fairchild Industries, which featured 7 instruments for observation of the solar activity.

The primary objective of the mission was the observation of high-energy solar phenomena, with particular emphasis on solar flares. Instruments were designed to monitor X-ray, gamma-ray, and ultraviolet emissions from the Sun, allowing detailed analysis of flare mechanisms and energy release processes. Continuous solar monitoring was intended to improve understanding of solar variability and its influence on near-Earth space.

A further goal was to correlate solar flare activity with associated effects in the heliosphere and Earth’s magnetosphere. Data from the satellite contributed to space weather research and to models of solar-terrestrial interactions.

The spacecraft was manufactured by Fairchild Industries and was the first satellite based on the Multimission Modular Spacecraft (MMS) bus, making it the first space craft designed for in space servicing. This standardized platform was developed to support a variety of low Earth orbit science missions. The MMS bus was later also used for Landsat 4 and 5, and UARS, demonstrating its adaptability and longevity.

Solar Maximum Mission was equipped with a three-axis stabilized attitude control system to ensure precise solar pointing. Power was supplied by solar arrays with rechargeable batteries for eclipse operations. Scientific payloads were mounted on modular interfaces compatible with the MMS design, simplifying integration and servicing.

SMM featured following instruments:

• Gamma Ray Spectrometer (GRS)
• Active Cavity Radiometer Irradiance Monitor (ACRIM)
• Coronagraph Polarimeter (CP)
• Hard X-Ray Burst Spectrometer (HXRBS)
• Hard X-Ray Imaging Spectrometer (HXIS)
• UV Spectrometer and Polarimeter (UVSP)
• X-Ray Polychromator (XRP)

The satellite operated in low Earth orbit, optimized for continuous solar observation and regular data downlink to ground stations. Redundant subsystems were incorporated to enhance mission reliability, although a critical failure occurred early in the mission.

In December 1980, the attitude control system failed due to a fuse failure. The satellite was repaired by astronauts of the 11th Shuttle mission, making it the first satellite to be repaired on orbit. It was originally planned to be returned to earth in 1990 by another Space Shuttle mission to be refurbished as the EUVE satellite, but these plans were finally cancelled. On 2 December 1989, Solar Maximum Mission re-entered Earth’s atmosphere and was destroyed over the Indian Ocean.