Calibration of the COBE FIRAS instrument
D. J. Fixsen, E. S. Cheng, D. A. Cottingham, R. E. jr Eplee, T. Hewagama, R. B. Isaacman, K. A. Jensen, J. C. Mather, D. L. Massa, S. S. Meyer, P. D. Noerdlinger, S. M. Read, L. P. Rosen, R. A. Shafer, A. R. Trenholme, R. Weiss, C. L. Bennett, N. W. Boggess, D. T. Wilkinson, E. L. Wright;
ApJ, 1994, 420, 457
ABSTRACT:The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite was designed to
accurately measure the spectrum of the cosmic microwave background radiation
(CMBR) in the frequency range 1-95/cm with an angular resolution of 7 deg.
We
describe the calibration of this instrument, including the method of obtaining
calibration data, reduction of data, the instrument model, fitting the model to the
calibration data, and application of the resulting model solution to sky
observations.
The instrument model fits well for calibration data that resemble sky
condition.
The method of propagating detector noise through the calibration process
to yield a covariance matrix of the calibrated sky data is described.
The
final uncertainties are variable both in frequency and position, but for a
typical calibrated sky 2.6 deg square pixel and 0.7/cm spectral element the
random detector noise limit is of order of a few times 10(exp -7) ergs/sq
cm/s/sr cm for 2-20/cm, and the difference between the sky and the best-fit
cosmic blackbody can be measured with a gain uncertainty of less than 3%.
KEYWORDS: background radiation, calibrating, cosmic background explorer satellite, mathematical models, michelson interferometers, angular resolution, data reduction, error analysis, fourier transformation, pixels, signal processing, signal to noise ratios
CODE: fixsen94