astronomy

STS-103

STS-103 is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand STS-103 rather than just read about it. In short: STS-103, the 96th launch of the Space Shuttle and the 27th launch of Space Shuttle Discovery, was Hubble Space Telescope Servicing Mission 3A ('SM3A'). It launched from Kennedy Space Center, Florida, on 19 December 1999 and returned on 27 December 1999 and was the last Shuttle mission of the 1990s.

Key takeaways

STS-103 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect STS-103 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of STS-103 from memory before moving on to harder problems.

Reference excerpt

STS-103, the 96th launch of the Space Shuttle and the 27th launch of Space Shuttle Discovery, was Hubble Space Telescope Servicing Mission 3A ('SM3A'). It launched from Kennedy Space Center, 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 Christmas 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 gyroscopes 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) in December 1993 and all six gyros were working during the second servicing mission (STS-82) 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 11.0 kilograms (24.3 lb) 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 computer previously used on Hubble. It weighs 32.0 kilograms (70.5 lb) 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 217 kilograms (478 lb) 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. The VIK modifies the charge cutoff voltage to a lower level to prevent battery overcharging and associated overheating. The VIK weighs about 1.4 kilograms (3.1 lb).

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 3.9 kilograms (8.6 lb) and is 14 by 8 by 2+3⁄4 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 11.3 kilograms (25 lb) 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 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, which was first used to wake up a flight crew during Apollo 15. 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.

Illustrations

Worked examples

Example 1 — a first encounter with STS-103

Start with the simplest possible case. Write down what STS-103 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to STS-103 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about STS-103 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of STS-103

In research: STS-103 appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses STS-103 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: STS-103 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1999 in Florida, December 1999, Hubble Space Telescope servicing missions, so understanding it makes those chapters shorter.
In everyday life: Look for STS-103 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study STS-103 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what STS-103 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain STS-103 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is STS-103 in simple terms?

Why does STS-103 matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study STS-103?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on STS-103.