The Solar Maximum Mission

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

(or SolarMax) was designed to investigate

Solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

phenomena, particularly

solar flares A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Stellar atmosphere, Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar partic ...

. It was launched on February 14, 1980. The SMM was the first satellite based on the

Multimission Modular Spacecraft Multi-mission Modular Spacecraft, also known as the MMS, was originally designed by NASA to serve the largest array of functions for the space program possible to decrease the cost of space missions. It was designed to operate in four distinct are ...

bus manufactured by Fairchild Industries, a platform which was later used for

Landsat 4 Landsat 4 is the fourth satellite of the Landsat program. It was launched on July 16, 1982, with the primary goal of providing a global archive of satellite imagery. Although the Landsat Program is managed by NASA, data from Landsat 4 was coll ...

and

Landsat 5 Landsat 5 was a low Earth orbit satellite launched on March 1, 1984, to collect imagery of the surface of Earth. A continuation of the Landsat Program, Landsat 5 was jointly managed by the U.S. Geological Survey (USGS) and the National Aerona ...

as well as the

Upper Atmosphere Research Satellite The Upper Atmosphere Research Satellite (UARS) was a NASA-operated orbital observatory whose mission was to study the Earth's atmosphere, particularly the protective ozone layer. The satellite was deployed from Space Shuttle Discovery, Space Shu ...

. After an

attitude control Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle or satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, ...

failure in November 1980 it was put in standby mode until April 1984 when it was repaired by a Shuttle mission. The Solar Maximum Mission ended on December 2, 1989, when the spacecraft re-entered the atmosphere and burned up over the Indian Ocean.

Instruments

Failure and repair

Capturing the Solar Maximum Mission satellite

The white-light coronagraph/polarimeter (C/P) took coronal images for about six months from March 1980 before suffering an electronics failure in September that prevented operation. In November 1980, the second of four fuses in SMM's

system failed, causing it to rely on its

magnetorquers A magnetorquer or magnetic torquer (also known as a torque rod) is a satellite system for attitude control, detumbling, and stabilization built from electromagnetic coils. The magnetorquer creates a magnetic dipole that interfaces with an ambient m ...

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. SMM was left in standby mode for 3 years. The first orbiting, uncrewed satellite to be repaired in space, SMM was notable in that its useful life compared with similar

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

was significantly increased by the direct intervention of a crewed space mission. During

STS-41-C STS-41-C (formerly STS-13) was NASA's eleventh Space Shuttle mission, and the fifth mission of Space Shuttle ''Challenger''. The launch, which took place on April 6, 1984, marked the first direct ascent trajectory for a Space Shuttle mission. ...

in April 1984, the Space Shuttle ''Challenger'' rendezvoused with the SMM, astronauts

James van Hoften James Dougal Adrianus "Ox" van Hoften (born June 11, 1944) is an American civil and hydraulic engineer, retired U.S. Navy officer and aviator, and a former astronaut for NASA. Personal data Van Hoften was born June 11, 1944, in Fresno, Califo ...

and George Nelson attempted to use the

Manned Maneuvering Unit The Manned Maneuvering Unit (MMU) is an astronaut propulsion unit that was used by NASA on three Space Shuttle missions in 1984. The MMU allowed the astronauts to perform untethered Extravehicular activity, extravehicular spacewalks at a dist ...

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 Trunnion 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 its blueprints. 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 with 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 fixture Grapple fixtures are used on spacecraft or other objects to provide a secure connection for a Articulated robot, robotic arm. North America The fixtures allowed the Space Shuttle, Space Shuttle's Canadarm (also known as the Shuttle Remote Manipul ...

s 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. Their successful work added five more years to the lifespan of the satellite. The mission was depicted in the 1985

IMAX IMAX is a proprietary system of High-definition video, high-resolution cameras, film formats, film projectors, and movie theater, theaters known for having very large screens with a tall aspect ratio (image), aspect ratio (approximately ei ...

movie '' The Dream Is Alive''.

Discovery of comets

10 comets were discovered in images from the SMM, all of which are members of the

Kreutz sungrazer The Kreutz sungrazers ( ) are a family of sungrazing comets, characterized by orbits taking them extremely close to the Sun at perihelion. At the far extreme of their orbits, aphelion, Kreutz sungrazers can be a hundred times farther from the Sun ...

group.

Findings

Significantly, the SMM's ACRIM instrument package showed that contrary to expectations, the Sun is actually brighter during the

sunspot Sunspots are temporary spots on the Sun's surface that are darker than the surrounding area. They are one of the most recognizable Solar phenomena and despite the fact that they are mostly visible in the solar photosphere they usually aff ...

cycle maximum (when the greatest number of dark 'sunspots' appear). This is because sunspots are surrounded by bright features called

faculae Facula ( faculae) is a bright spot on the surface of a planet or a star. It may refer to * Solar facula * * Bright spots on Ceres * * * * {{disambig ...

, 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.

End of mission

SMM's orbit slowly decayed due to atmospheric drag taking it down into denser regions. The

March 1989 geomagnetic storm The March 1989 geomagnetic storm occurred as part of severe to extreme solar storms during early to mid March 1989, the most notable being a geomagnetic storm that struck Earth on March 13. This geomagnetic storm caused a nine-hour outage of Hyd ...

was reported to have led to SMM dropping half a kilometre at the start of the storm and 5 kilometres over the whole period. The satellite eventually lost attitude control on November 17, 1989, and re-entry and burn-up occurred on December 2, 1989, over the Indian Ocean.

References

External links

HEASARC
SMM
Marshall Space Flight Center
, SMM

Total Solar Irradiance
ACRIM {{Authority control Spacecraft launched in 1980 Satellites formerly orbiting Earth Solar telescopes Spacecraft launched by Delta rockets Spacecraft which reentered in 1989 Solar space observatories NASA satellites orbiting Earth