Abstract
The High-Resolution Infrared Radiation Sounder (HIRS) has been operational since 1975 on different satellites. In spite of this long utilization period, the available information about some of its basic properties is incomplete or contradictory. We have approached this problem by analyzing intrusions of the Moon in the deep space view of HIRS/2 through HIRS/4. With this method we found: (1) The diameters of the field of view of HIRS/2, HIRS/3, and HIRS/4 have the relative proportions of 1.4 ° to 1.3 ° to 0.7 ° with all channels; (2) the co-registration differs by up to 0.031 ° among the long-wave and by up to 0.015 ° among the shortwave spectral channels in the along-track direction; (3) the photometric calibration is consistent within 0.7% or less for channels 2–7 (1.2% for HIRS/2), similar values were found for channels 13–16; (4) the non-linearity of the short-wavelength channels is negligible; and (5) the contribution of reflected sunlight to the flux in the short-wavelength channels can be determined in good approximation, if the emissivity of the surface is known.
Highlights
The High-resolution Infra-Red Radiation Sounder (HIRS) performs temperature/humidity sounding on satellites in sun-synchronous orbit since the seventies
We give in the following several illustrations of how lunar intrusions in the deep space view can serve as diagnostic tool for an infrared sounder
In the example of the pair HIRS/2 and HIRS/3 mentioned above we find a value of 1.031 for the ratio of the average radiance of the Moon measured with HIRS/2 and HIRS/3, but 1.007 for the ratio of the corresponding brightness temperatures
Summary
The High-resolution Infra-Red Radiation Sounder (HIRS) performs temperature/humidity sounding on satellites in sun-synchronous orbit since the seventies. It flies as well on TIROS-N, Metop-A, and Metop-B In all these years the instrument evolved to HIRS/4 and has accumulated a large set of observations relevant to the study of long-term variations of temperature and upper tropospheric humidity (UTH), amongst other things. A trend analysis over three decades of HIRS channel 12 measurements, trying to find changes in tropical UTH, is described for example in [2]. Their investigation, was hampered by significant inter-satellite biases, the reason for which was not identified.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
