The energy started by the pickoff mirror in its 3 1/2 years in space is
approximately equal to the amount of energy from 2 orbits of Earth exposure
during the Servicing Mission (because of the solid angle of the Earth).
Possible Out gassing Sources: Optical Telescope
Assembly and Fine Guidance Systems
- The Hub Space Telescope contamination would
likely come from either the optical telescope assembly or the three fine
guidance sensors.
- Some FGS components were not baked out.
- FGS and OTA subsystems were baked out until
QCM at 50-55 degrees Fahrenheit for 36 hours
- FGSs had verification test run with QCM at hub
facing aperture, QCM 18 degrees Fahrenheit below on-orbit temperature of
70 degrees Fahrenheit plus or minus 5 degree, 8 hours at 1 Hz/hr.
- Though science instruments also faced the hub,
they were certified at -20 degrees Celsius at 1 Hz/hr (much cleaner) and
have only a small aperture facing the hub.
- FGSs do have a few-inch gap running across the top
of them in the hub.
This
is picture of the Hub Space Telescope
On-Orbit Data Since Servicing Mission
- GHRS is the most reliable on-orbit UV data for
judging UV degradation to COSTAR.
- FOS data agrees with GHRS data.
- WF/PC-II data is expected December, 1994.
- Small degradation is expected since out gassing in
HST has been going on for four years. Therefore, the number of molecules is
depleted.
Conclusions/Summary
- Based on results from well-controlled optical
surfaces the contaminant appears to be a UV-deposited organic with soluble
and non-soluble components.
- Source of UV is believed to be Earth albedo.
- Results from non-optical surfaces are inconclusive and additional samples are currently being
analyzed.
- Team is addressing question of whether any
surfaces that did not see UV Earth albedo were contaminated.
- Team is addressing issue of whether deposition
occurred in HST bay during 3.5 years in space or during the Servicing
Mission.
- Additional samples from the High Speed
Photometer exterior are being collected and are expected to help resolve
these issues.
- Based on existing data, scientific instruments
currently in HST appear to have minimal UV degradation.