SOFIA eNewsletter for Scientists
SOFIA Telescope Development Highlights

     vol. 2    October 1, 2001
      This eNewsletter is intended for the scientific community. If you would like to receive our quarterly newsletter, please contact SOFIA@usra.edu

SOFIA Bearing Sphere

Telescope Suspension Assembly

The Rotational Isolation System (RIS) was "floated" for the first time in August at MAN Technologie in Augsburg, and appeared to work well. This spherical hydrostatic bearing will support the telescope while isolating it from aircraft angular excursions and allowing smooth movement on the sky. The RIS is basically a cast iron sphere 1.2 m in diameter floating on a ~30 micron thick oil film, which is supplied via ringed sockets from an external source under a pressure of ~50 bars. Thus the spherical bearing, with telescope attached, glides on the oil film in a gap between the sockets and the sphere. The mechanical, flow rate, and temperature tolerances of the entire system are critical to achieving the required sub-arcsecond telescope pointing stability.

Tests now in progress will verify the load carrying capability of the RIS, measure its friction, validate the thermal analyses, and calibrate various sensors including those measuring the oil gap and the bearing sphere attitude.


Spherical bearing installed in support assembly


 



Zerodur f/1.28, 2.7 m diameter Primary Mirror
Telescope Optics

Kayser-Threde Gmbh in Munich have subcontracted the lightweighting and polishing of the f/1.28, 2.7 m Zerodur primary telescope mirror to SAGEM (formerly REOSC) near Paris, and the construction of the 2kg, 0.35 m silicon carbide secondary mirror to ASTRIUM in Toulouse. The mirrors have been optically finished and tested in the past four months. Their combined performance would permit nearly diffraction-limited imaging at visible wavelengths, in the absence of the unavoidable ~arcsecond seeing caused by Mach 0.85 air flowing over the open-port telescope cavity. Integration of the optical elements into the metering structure, which along with the RIS is now being built up in Augsburg, is scheduled to occur during the coming year.

Silicon Carbide, 35 cm diameter Secondary Mirror


Program Description

SOFIA's Boeing 747 SP and 2.7 m telescope will enable unprecedented astronomical observations
at most infrared and submillimeter wavelengths. The program is cooperatively sponsored by NASA,
with the project office at Ames Research Center, and by the German Aerospace Center, DLR, in Bonn.
On the current schedule, SOFIA will begin operations under prime contractor USRA in late 2004.

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SOFIA Science Instruments:
http://sofia.arc.nasa.gov/observatory/instruments/sci_instruments.html

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http://sofia.arc.nasa.gov/News/news_updates.html