Servicing Mission 3A
(SM3A)

NASA has a call to action when four of Hubble’s six gyros failed.

mission type

Servicing Mission

shuttle mission

STS-103

Launch

Dec 19, 1999

duration

7 days

Astronaut in a white space suit tethered to the Hubble Space Telescope floating in space. — Steven L. Smith, STS-103 payload commander, waves to a crewmate located inside the Space Shuttle Discovery's cabin during the first spacewalk of NASA's third servicing mission to the Hubble Space Telescope (HST).
NASA

Image showing astronaut holding the Pistol Grip Tool, which looks like an electric screwdriver. The astronaut's face is visible through his visor, he is smiling. He stands next to a large gold box with a bit of the Shuttle visible behind him. — Astronaut Claude Nicollier, mission specialist from the European Space Agency (ESA), works at a storage enclosure, using one of the Hubble powertools, during the second of three STS-103 extravehicular activities (EVA).
NASA

Overview

Originally conceived as a mission of preventive maintenance scheduled for June 2000, Servicing Mission 3 turned more urgent when three of Hubble’s gyros failed. Then on November 13, 1999, when the fourth of Hubble’s six gyros failed, the telescope temporarily closed its eyes on the universe. Hubble’s gyroscopes measure the speed at which the telescope is turning. The telescope cannot safely turn or lock on to new targets without them. A wheel, mounted inside the gyroscope spins at a constant rate of 19,200 revolutions per minute. Electronics within the gyroscope detect very small movements of the axis of the wheel and communicate this information to Hubble’s central computer. Unable to conduct science without three working gyros, Hubble entered a state of dormancy called safe mode – Hubble essentially "went to sleep" while it waited for help.

Two astronauts work inside the bottom of Hubble while flying over the earth.

Astronauts Steven L. Smith and John M. Grunsfeld, appear as small figures in this wide-angle photograph taken during an extravehicular activity (EVA) in December 1999. On this spacewalk they replaced the rate sensor units (RSUs, or gyroscopes) inside the Hubble Space Telescope.

NASA

Quick Facts

Number of Orbits: 119
Miles traveled: 3.2 million
The third time in the U.S. Space Program that a crew spent Christmas in space

In an effort to swiftly bring Hubble back to life, NASA decided to split Servicing Mission 3 into two parts – Servicing Mission 3A (SM3A) and Servicing Mission 3B (SM3B) – quickly approving, developing, and executing SM3A in a record seven months!

The first spacewalk or EVA (extravehicular activity) included replacing the telescopes three Rate Sensor Units, each containing two gyroscopes. Astronauts Steven Smith and John Grunsfeld also installed six battery voltage/temperature improvement kits between Hubble’s solar panels and its six 10-year-old batteries. The kits, which are the size of cellphones, prevent the batteries from overheating or overcharging. The 8-hour, 15-minute spacewalk was the second longest spacewalk in history.

During the mission’s second 8-hour EVA, astronauts Michael Foale and Claude Nicollier installed a faster, more powerful, main computer. The new computer was 20 times faster than Hubble’s old one. They also installed a new 550-pound fine guidance sensor.

The third and final EVA saw astronauts Smith and Grunsfeld teaming up for another 8-hour spacewalk to install a new transmitter that sends scientific data from Hubble to the ground. It replaced one that failed in 1998. They also installed a next-generation solid-state data recorder, replacing an older mechanical reel-to-reel recorder.

In a fitting gesture, SM3A astronauts released the newly restored telescope back to its orbit on Christmas Day.

Servicing Mission 3A Interactive Timeline

Meet the Hubble SM3A Astronauts

All Hubble Astronauts

Curtis Brown

Mission Commander

Scott Kelly

Pilot

Official astronaut portrait of Jean-Francois Clervoy.

Jean-François Clervoy

Mission Specialist

Michael Foale

Mission Specialist

John Grunsfeld

Mission Specialist

Steven Smith

Mission Specialist

Claude Nicollier

Mission Specialist

Hubble Servicing Mission

STS-103 Mission Facts

STS-103 restored the Hubble Space Telescope to working order and upgraded some of its systems, allowing the decade-old observatory to get ready to begin its second scheduled decade of astronomical observations.

Explore STS-103 Details

View from out of a shuttle window of the Hubble Space Telescope in space with the Earth in the background.

This image shows the Hubble Space Telescope (HST) being berthed in Discovery's payload bay on Dec. 21, 1999. The photo was downlinked at the completion of the third HST servicing mission's first spacewalk on the following day by the busy STS-103 astronauts.

NASA