ASTROCAM
Until recently, low-background Indium Antimonide arrays (the best quality imaging devices for 1-5 microns) were not available in formats larger than 256 x 256. In a program funded by ONR and NSF, under the supervision of USNO scientists, a 1024 x 1024 format array was developed by Santa Barbara Research Corporation for the USNO parallax program and for the astrophysics community at large. NRL scientists and engineers designed the optics and specified the electronics and software for a cryogenic camera optimized for collaborative infrared astrometric and astronomical observations on the USNO 1.5-meter telescope in Flagstaff, Arizona. The collaboration began in April 1994. The instrument was built by Mauna Kea Infrared, Inc. with a tolerance analysis carried out at Yerkes Observatory and delivered to USNO in August 1999.
ASTROCAM is currently used for the USNO parallax program to measure the annual parallax of objects classified as brown dwarfs, only recently discovered by astronomers after years of unsuccessful searches. The distances to hundreds of these objects can then be determined and true luminosities inferred. Infrared cameras with large format sensitive arrays provide the capability to detect the faint, red T and L dwarfs and simultaneously sufficient numbers of reference background stars for the parallax measurements. It is also being used by NRL infrared-astronomers to directly measure the supernova rate in dusty starburst galaxies. Optical measurements underestimate the supernova rate in these galaxies, since supernovae are preferentially found in obscuring clouds of gas and dust. The supernova rate is important for understanding the abundance of metals in the universe and to determine the upper mass limit in starbursts (see publications below).
|
|
A CAD drawing of ASTROCAM, showing its all-reflective Offner-based re-imager design and its pupil imaging refractive optics. |
2003, in Astronomical Telescopes and Instrumentation: Instrument Design and Performance for Optical/Infrared Ground-Based Telescopes, Proc. SPIE 4841, eds. Masanori Iye, Alan F. Moorwood, p. 564. ©2003 The Society for Photo-Optical Instrumentation Engineers.