FGE Instrument Description

The FGE is a flexible solar observatory. Its capabilities are summarized in this table.

The basic design of the FGE gondola was derived from a payload (Exite instrument) developed by the Harvard/Smithsonian Center for Astrophysics (CFA). The frame is bolted together from standard aluminum angle. This approach was adopted to simplify both material procurement and construction. The structure is strong enough to support the 4400-lb weight of the instrumentation, telescope, NSBF's Support Instrument Package (SIP), ballast and solar panels, even under a design load of 10 g, as well as being rigid enough to allow stable pointing to at least 10 arcsec. CAD drawings of the gondola can be found in this page.

The command and control electronics and the two tape drives are housed in 4 pressure vessels, and with the power system's batteries, reside on the mezzanine level. During flight, thermal blankets protect this area from direct sunlight.

The main telescope (MT), the pointing telescope (PT) , and a pressure vessel housing the optical analysis stages are mounted together and pivoted around the elevation axis, driven by a torque motor.

A key component, at the top of the gondola, is the momentum transfer unit (MTU). The MTU provides (1) the means for pointing in azimuth (a motor provides torque between the frame and a reaction wheel, simultaneously accelerating the frame in one direction and the wheel in the other); (2) a means for transferring momentum from the frame+reaction wheel system into the flight train (a motor provides torque between the frame and the main titanium drive shaft); and (3) the support and attachment point between the gondola and the flight train. One change to CFAs MTU design was the provision of a path through a slip ring and the main shaft for a cable to link the flight train with SIP, required for Antarctic operation.

The FGE telescope was donated by the Strategic Defense Initiative Organization.
Other important FGE components are:

• 50 mm refracting telescope for tracking.
• 1024 x 1534-pixel Kodak Megaplus CCD camera - 20 MByte/s read rate.
• Exabyte tape loaders with 100 GByte capacity.
• 0.16 Å lithium-niobate etalon filter coated for 6000 - 6600 Å operation.
• Six thin-film 1.25 Å prefilters for wavelength selection.
• Two liquid-crystal polarization modulators.
• Lateral effect diode to detect pitch and yaw to ~ 0.3 arcsec.
• Image motion compensation of 0.1 arcsec at the focal plane.

• Two 6 ft x 12 ft solar panel arrays - 1000 W capacity.
• Reaction wheel and momentum transfer unit for azimuth pointing control.
• Ground support computers, recorders and transmitters.
• On-board S-band transmitter - 0.5 Mbits/s (line of sight).