IRAS Explanatory Supplement
VI. Flux Reconstruction and Calibration

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Chapter Contents | Introduction | Authors | References
Table of Contents | Index | Previous Chapter | Next Chapter

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Chapter VI Contents

1. Processing - Removal of Telescope Transfer Function
   1. Digital Electronics
   2. Analog Electronics Amplifiers
   3. Trans-impedance Amplifier
   4. Removal of Coherent Detector Noise
   5. Feedback Resistor
   6. Summary
2. Determination of Relative Flux
   1. Overall Procedure to Determine Relative Photometry
   2. Photometry of Point Sources and Small Extended Sources
   3. Photometry of Extended Emission
      1. Determination of F[TFPR]
      2. Determination of the TFPR Annual Variation
   4. Problems
      1. Rejected Internal Reference Source Flashes
      2. Radiation
      3. Photon Induced Responsivity Enhancement
         1. Point Sources
         2. Extended Emission
      4. Variation of Frequency Response with Total Flux
3. Absolute Calibration
   1. General Philosophy
   2. Point Source Calibration
      1. Stellar Calibration
      2. Asteroid Calibration
      3. Estimated Accuracy
   3. Color Corrections
   4. Absolute Calibration of Extended Emission
4. Comparison of IRAS Observations with Ground Based Observations

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Introduction

Three quite separate functions must be performed in order to reconstruct the flux of a source from the telescope data stream. first, the effects of the telescope transfer function must be removed from the data. Second, the results must be transferred to relative photometric units. In the case of IRAS, this amounted to establishing the relationship between source amplitudes observed during the survey scans and outputs of flashes of the internal reference source. Third, the relative photometry must be put on an absolute scale, i.e., the flashes of the internal reference source must be calibrated in an absolute sense.

In the following discussion, the processing by which the signal received at the ground station was converted to the effective detector current is described, followed by the description of the process by which the relative and, finally, the absolute photometry was achieved.

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Authors:

G. Neugebauer, S. Wheelock, F. Gillett, H.H. Aumann, T.N. Gautier, F.J. Low, P. Hacking, M. Hauser, S. Harris, P. Clegg.

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References:

Allen, D.A. 1970, Nature, 227, 158.
Allen, D.A., 1971, in Physical Studies of Minor Planets, editor T. Gehrels, Univ. Ariz, Press, p. 41.
Bell, R., 1984 private communication.
Gustafsson, Bell, Ericksson, Nordlund, 1975, Astr. Ap., 42, 407
Hauser, M., et al. 1984, Ap.J.(Lett.) 278, L15.
Hildenbrand, R.H., Lowenstein, R.F., Harper, D.F., Orton, G.S., Keene, J., and Whitcomb, S. 1984, pre-print.
Jones, T.J., and Morrison, D. 1974, A.J. 79, 892.
Kurucz 1979, Ap.J. (Suppl.), 40, 1.
Lebofsky 1984, personal communications
Low, F.J., et al. 1984, Ap.J.(Lett.), 278, L19.
Morrison, D. 1973, A.J., 194, 203.
Rieke, G.H., Lebofsky, M., and Low, F.J. 1984, preprint.
Tokunaga, A. 1984, A.J., 89, 172.
Vernazza, J.E., Avrett, E.H., and Loeser, R. 1976, Ap.J. (Suppl.), 30,1.
Zellner, B., 1979 in Asteroids, editor T. Gehrels, Univ. Ariz. Press, p. 1011.

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