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Astrophysics Science Division | Sciences and Exploration

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SM3A Additional Mission Information and Timeline

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Hubble Extravehicular Activities (EVA) Timeline

As a result of the weather-delayed launch, the mission has been shortened to 3 EVA days. This will guarantee that the Discovery will be safe from all possible Y2K problems under all contingency return situations.

NASA calls a spacewalk an "Extra-Vehicular Activity", or EVA. Each of the EVA servicing periods is an EVA Day, although these "days" span two "Flight Days". For example, EVA Day 1 begins two days and 19 hours into the mission, and it ends in the second hour of the third mission day. The tasks are arranged in order of importance and efficiency. The spacewalkers will work in teams of two, with each pair going out on alternating days.

December 18, 1999 Proposed EVA plan

Original EVA Plan

EVA Day 1
The first team will replace Hubble's three Rate Sensor Units (RSUs), each containing two gyros. They will also install Voltage/Temperature Improvement Kits (VIKs) on Hubble's six batteries.
2 Days, 18 Hours, 45 Minutes
EVA Day 1 Movie (11,400 KB) (77 KB)

EVA Day 2
The second team will replace the telescope's central computer and a Fine Guidance Sensor (FGS).
3 Days, 19 Hours
EVA Day 2 Movie
(11,800 KB) (85KB)

EVA Day 3
The first pair of spacewalkers goes out again to replace a transmitter and a data recorder, upgrade electronics, and begin reinforcing Hubble's thermal skin.
4 Days, 19 Hours

EVA Day 4
The second team returns to Hubble to finish attaching the new thermal protection.
5 Days, 19 Hours
EVA Day 4 Movie (11,300 KB) (178 KB)



HST Command Plan

The Servicing Mission Command Plan is the set of procedures used by Hubble's ground control team to prepare the telescope for servicing, test the newly installed equipment, and release the telescope back into orbit.

Shortly after launch, the Space Telescope Operations Control Center (STOCC) team will begin transitioning the telescope from normal science operations to a "ready for servicing" condition. They will command Hubble to its capture attitude and configure it for rendezvous with Discovery.

In preparation for capture and berthing, the STOCC will instruct Hubble's aperture door to close and the high gain antennas to be stowed. Immediately after the astronauts install the new equipment, they will move to a safe location. Then, the STOCC will test the hardware to determine if more work is needed. Later, while the crew sleeps, the STOCC team will perform more detailed checkouts. Finally, at the mission's end, ground controllers will prepare Hubble for its return to normal operations.

Servicing Mission Integrated Timeline

The Servicing Mission Integrated Timeline (SMIT)

The Servicing Mission Integrated Timeline (SMIT) is a detailed, minute-by-minute schedule of mission activities. It simultaneously shows all major work performed by the astronauts and the ground controllers. The timeline also includes several time measures (mission elapsed time, orbit number, UT, etc.), the position of the Shuttle and Hubble, and the astronauts' sleep time. The servicing team relies on this script-like schedule to track mission progress.

sample SMIT page
Sample SMIT page

How to Read the Integrated Timeline

TIME: The clock begins at launch. The time is shown in Greenwich Mean Time (GMT) and Mission Elapsed Time (MET).

  • For GMT, the day of the year is shown in the margin.
  • For MET, the day of mission is shown in the margin.

ORBIT#: When the Shuttle begins preparations for rendezvous with Hubble, the ORBIT# will be that of the Shuttle. Prior to these preparations, the ORBIT# will be that of Hubble.

DAY/NIGHT: The shaded areas show when Hubble is in the Earth's shadow. The light areas represent Hubble's daytime.

SAA: Time in the South Atlantic Anomaly. The SAA is an area of intense radiation above the coast of Argentina. As the Shuttle and other satellites pass through it, the SAA can disrupt electronics and communications signals. It is the southern point of the Van Allen Belt.

HST ATTITUDE: How Hubble is positioned.

ORBITER ATTITUDE: How the Shuttle is positioned.

CREW SCHEDULE: Major crew activities, such as preparing for a spacewalk and sleeping.

ORBITER, CREW, SSE: The Shuttle and astronaut activities relating to Hubble and the Space Support Equipment (SSE).

FUNCTIONAL COMMAND: A description of the command and verification activities performed by Hubble's ground controllers. A legend in the margin shows the different types of commands.

TLM FORMAT: The telemetry format requirements for the engineering and science channels.

TDRSS/I&C: The area of communication coverage and the Zone Of Exclusion (ZOE).

GROUND SYSTEM ACTIVITIES: The major activities within the Space Telescope Operations Control Center (STOCC).

MAJOR EVENTS: An overview of all major activities in space and on the ground.


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