The High-resolution Infrared Radiation Sounder (HIRS/4) provides calibrated vertical profiles of temperature and humidity; information on cloud cover, cloud top height, cloud top temperature and cloud phase, as well as surface albedo.

HIRS Instrument (tn)

What is HIRS?

HIRS is a 20-channel infrared scanning radiometer that performs operational atmospheric sounding.

HIRS has 19 infrared channels (3.8-15 µm) and one visible channel. The swath width is 2160 km, with a 10 km resolution at nadir.

IR calibration of the HIRS/4 is provided by programmed views of two radiometric targets mdash; the warm target, mounted on the instrument baseplate, and a view of deep space. Data from these views provides sensitivity calibrations for each channel at 256 second intervals, if commanded. Internally generated electronic signals provide calibration and stability monitoring of the detector amplifier and signal processing electronics.

HIRS uses CO2 absorption bands for temperature sounding (CO2 is uniformly mixed in the atmosphere). HIRS also measures water vapour, ozone, N2O and cloud and surface temperatures.

HIRS/4 is manufactured by ITT Exelis in Fort Wayne, Indiana under contract to NASA. For more in-depth information, see the ATOVS Level 1b Product Guide and the NOAA KLM User's Guide, Section 3.2.2

NOTE: Metop-C does not carry the HIRS instrument

HIRS Summary Budget

HIRS Summary Budget
Scan Rate 6.4secs
Scan Type Stop and stare
Pixel IFOV 0.69° (circular)
IFOV size at Nadir 10 km
Sampling at Nadir 26 km
Earth View Pixels/Scan 56
Swath ± 49.5°
Swath width ± 1092 km
Spectral Range 0.69 to 15 µm
Lifetime Five years (three years design life)
Power 24 W
Size 410 mm x 460 mm x 690 mm
Mass 35 kg
Data rate 2.88 kbps
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