STS-103, the 96th launch of the

Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...

and the 27th launch of

Discovery Discovery may refer to: * Discovery (observation), observing or finding something unknown * Discovery (fiction), a character's learning something unknown * Discovery (law), a process in courts of law relating to evidence Discovery, The Discovery ...

'', was a

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

servicing mission. It launched from

Kennedy Space Center The John F. Kennedy Space Center (KSC, originally known as the NASA Launch Operations Center), located on Merritt Island, Florida, is one of the NASA, National Aeronautics and Space Administration's (NASA) ten NASA facilities#List of field c ...

, Florida, on 19 December 1999 and returned on 27 December 1999 and was the last Shuttle mission of the 1990s. It was the only mission to span through

Christmas Christmas is an annual festival commemorating Nativity of Jesus, the birth of Jesus Christ, observed primarily on December 25 as a Religion, religious and Culture, cultural celebration among billions of people Observance of Christmas by coun ...

after being delayed by 13 days for technical and weather reasons.

Crew

Space walks

*'' Smith and Grunsfeld '' – EVA 1 *EVA 1 start: 22 December 1999 – 18:54 UTC *EVA 1 end: 23 December 1999 – 03:09 UTC *Duration: 8 hours, 15 minutes *'' Foale and Nicollier '' – EVA 2 *EVA 2 start: 23 December 1999 – 19:06 UTC *EVA 2 end: 24 December 1999 – 03:16 UTC *Duration: 8 hours, 10 minutes *'' Smith and Grunsfeld '' – EVA 3 *EVA 3 start: 24 December 1999 – 19:17 UTC *EVA 3 end: 25 December 1999 – 03:25 UTC *Duration: 8 hours, 8 minutes

Crew seat assignments

Mission highlights

The primary objective of STS-103 was the Hubble Servicing Mission 3A. STS-103 had four scheduled Extravehicular Activity (EVA) days where four crew members worked in pairs on alternating days to renew and refurbish the telescope. NASA officials decided to move up part of the servicing mission that had been scheduled for June 2000 after three of the telescope's six

gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining Orientation (geometry), orientation and angular velocity. It is a spinning wheel or disc in ...

s failed. Three gyroscopes must be working to meet the telescope's very precise pointing requirements, and the telescope's flight rules dictated that NASA consider a "call-up" mission before a fourth gyroscope failed. Four new gyros were installed during the first servicing mission (

STS-61 STS-61 was NASA's first Hubble Space Telescope servicing mission, and the fifth flight of the Space Shuttle Endeavour, Space Shuttle ''Endeavour''. The mission launched on December 2, 1993, from Kennedy Space Center (KSC) in Florida. The missi ...

) in December 1993 and all six gyros were working during the second servicing mission (

STS-82 STS-82 was the 22nd flight of the Space Shuttle Space Shuttle Discovery, ''Discovery'' and the 82nd mission of the Space Shuttle program. It was NASA's second mission to service the Hubble Space Telescope, during which ''Discovery's'' crew repai ...

) in February 1997. Since then, a gyro failed in 1997, another in 1998 and a third in 1999. The Hubble team believed they understood the cause of the failures, although they could not be certain until the gyros were returned from space. Having fewer than three working gyroscopes would have precluded science observations, although the telescope would have remained safely in orbit until a servicing crew arrived. Hubble's gyros spin at a constant rate of 19,200 rpm on gas bearings. This wheel is mounted in a sealed cylinder, which floats in a thick fluid. Electricity is carried to the motor by thin wires (approximately the size of a human hair). It is believed that oxygen in the pressurized air used during the assembly process caused the wires to corrode and break. The new gyros were assembled using nitrogen instead of oxygen. Each gyroscope is packaged in a Rate Sensor assembly. The Rate Sensors are packaged in pairs into an assembly called a Rate Sensor Unit (RSU). It is the RSUs that the STS-103's astronauts changed. The RSUs each weigh and are 12.8 by 10.5 by 8.9 inches (325 by 267 by 226 mm) in size. In addition to replacing all six gyroscopes on the December flight, the crew replaced a Fine Guidance Sensor (FGS) and the spacecraft's computer. The new computer reduced the burden of flight software maintenance and significantly lowered costs. The new computer was 20 times faster and had six times the memory of the

DF-224 The DF-224 is a space-qualified computer used in space missions from the 1980s. It was built by Rockwell Autonetics. As with many spacecraft computers, the design is very redundant, since servicing in space is at best difficult and often impossi ...

computer previously used on Hubble. It weighs and is 18.8 by 18 by 13 inches (478 by 457 by 330 mm) in size. The FGS installed was a refurbished unit that was returned from Servicing Mission 2. It weighs and is 5.5 by 4 by 2 feet (1.68 by 1.22 by 0.61 m) in size. A voltage/temperature improvement kit (VIK) was also installed to protect spacecraft batteries from overcharging and overheating when the spacecraft goes into

safe mode Safe mode is a diagnosis, diagnostic mode of a computer operating system (OS). It can also refer to a mode of operation by application software. ''Safe mode'' is intended to help fix most, if not all, problems within an operating system. It is a ...

. The VIK modifies the charge

cutoff voltage In electronics, the cut-off voltage is the voltage at which a battery is considered fully discharged, beyond which further discharge could cause harm. Some electronic devices, such as cell phones, will automatically shut down when the cut-off vol ...

to a lower level to prevent battery overcharging and associated overheating. The VIK weighs about . The repair mission also installed a new S-Band Single Access Transmitter (SSAT). Hubble has two identical SSATs onboard and can operate with only one. The SSATs send data from Hubble through NASA's Tracking Data Relay Satellite System (TDRSS) to the ground. The new transmitter replaced one that failed in 1998. The SSAT weighs and is 14 by 8 by inches (356 by 203 by 70 mm). A spare solid state recorder was also installed to allow efficient handling of high-volume data. Prior to the second servicing mission, Hubble used three 1970s-style reel-to-reel tape recorders. During the second servicing mission, one of these mechanical recorders was replaced with a digital solid state recorder. During this mission a second mechanical recorder was replaced by a second solid state recorder. The new recorder could hold approximately 10 times as much data as the old unit (12 gigabytes instead of 1.2 gigabytes). The recorder weighs and is 12 by 9 by 7 inches in size. Finally, the EVA crew replaced the telescope's outer insulation that had degraded. The insulation is necessary to control the internal temperature on the Hubble. The New Outer Blanket Layer (NOBL) and Shell/Shield Replacement Fabric (SSRF) help protect Hubble from the harsh environment of space. It protects the telescope from the severe and rapid temperature changes it experiences during each 90 minute orbit as it moves from sunlight to darkness. STS-103 also carried hundreds of thousands of student signatures as part of the Student Signatures in Space (S3) program. The unique project provided elementary schools (selected on a rotating basis) with special posters to be autographed by students, then scanned onto disks and carried aboard a NASA Space Shuttle mission. It was the ''Discovery's'' last solo spaceflight. All later missions by Discovery were

International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...

missions. Astronaut John Grunsfeld, who was one of the mission specialists on this mission, brought a " Planet Mars Flag" aboard ''Discovery''.

Wake-up calls

NASA began a tradition of playing music to astronauts during the

Gemini program Project Gemini () was the second United States human spaceflight program to fly. Conducted after the first American crewed space program, Project Mercury, while the Apollo program was still in early development, Gemini was conceived in 1961 and ...

, which was first used to wake up a flight crew during

Apollo 15 Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the Apollo program and the fourth Moon landing. It was the first List of Apollo missions#Alphabetical mission types, J mission, with a longer stay on the Moon and a greate ...

. Each track is specially chosen, often by their families, and usually has a special meaning to an individual member of the crew, or is applicable to their daily activities.

References

External links

NASA mission summary

{{Use American English, date=January 2014 Spacecraft launched in 1999 Hubble Space Telescope servicing missions Space Shuttle missions December 1999 1999 in Florida Spacecraft which reentered in 2009