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Last Updated Jan 2001
Copyright © 2001 The Association of Universities for Research in Astronomy, Inc. All Rights Reserved.
Plate Vault
Room 135 of the Muller building is used for storage of the GSSS photographic plate collection and for examination of these plates. Entrance is secured by means of the same access card that controls access to the Science Mission Operations Room, and direct access to the plates is restricted to trained CASB plate handlers only. Facilities include:- Plate cabinets. The plates are stored in protective Tyvek envelopes on edge in enamel/steel closed cabinets approximately 84" H x 36" W x 20" D. There are four shelves in each cabinet. Metal umbrellas overhang the plate cabinets for protection in case of water leaks.
- Three light tables, of varying size and brightness. One includes a mounted binocular microscope.
- General utility XTerminal
- Compressed air supply for cleaning
- Film cabinet. Film copies of the POSS-II and SES F surveys are stored in a hanging cabinet by means of Versatec strips, so the films hang freely
- Hardware cabinets, containing spare parts and tools used in maintaining the GAMMA machines.
GAMMA Rooms
The two GAMMA rooms are essentially identical with dimensions of 9 x 11 feet. The GAMMA machines are positioned near the rear of the rooms on a foundation that is separated from the rest of the building, for vibrational insulation. The operator normally works in the space in front of the GAMMA for plate mounting and dismounting. Each scanning machine has a dedicated VAXStation 4000 with ?? Gbytes of magnetic disk space and an 8mm stacking tape drive for data archive. The VAXStation is used both for machine control and for preliminary quality assurance of the scan data. Each room is equipped with a dimmer switch to optimally control room lighting during scan setup, and is protected from light leaks during scanning.Environmental Controls
The plate vault area, including the two GAMMA rooms, is a controlled location, in terms of both security and environment.Humidity and Temperature Controls
The temperature and humidity levels of all three rooms are automatically recorded on the environmental charts. Certain fluctuations are predictable and expected: when there are people in the GAMMA rooms for any length of time, or when the floor is being washed. These can be tolerated or, if need be, corrected. Unexplained fluctuations should be brought to the attention of ST ScI facilities staff at once, so that they can be corrected.For plate safety, the humidity must be kept below 60%. For scanning accuracy, the temperatures of the vault and GAMMA rooms must be the same within +/- 2 degrees F.
Air Handling System and Filters
To ensure that the environmental standards are met in the plate vault and GAMMA rooms, a separate air handling system has been installed. The circulation of the air is described below.Return air from the CASB operations room is mixed with additional outside air, i.e., make up air, supplied at 200 cubic feet per minute from a separate air intake on the roof of the ST ScI. The air flows through a set of three filters. The pre-filter removes large particles; the charcoal filter removes gaseous impurities; and the Hepa filter removes fine particles. The air then passes through cooling coils which dehumidify it. The supply fan is set to maintain sufficient pressure in the system to cause an outward draft around the plate vault doors. The humidifier and reheat coils bring the air to the correct humidity and temperature before it reenters the vault area.
Alarm System
The GSSS work area, plate vault,
and GAMMA rooms are on a separate fire alarm system
from the rest of the building. Because the plates are susceptible to water
damage, a halon system has been installed in these areas.