BackForwardInstrument:  HIRS/4 

Instrument details
Acronym HIRS/4
Full name High-resolution Infra Red Sounder / 4
Purpose Temperature/humidity sounding
Short description 20 channels (including one VIS) [see detailed characteristics below]
Background Evolution of HIRS/3 on NOAA 15/16/17. Operations on NOAA-18 stopped in 2009. HIRS is part of the ATOVS sounding instrument suite (Advanced TIROS Operational Vertical Sounder)
Scanning Technique Cross-track: 56 steps of 26 km s.s.p., swath 2200 km - Along-track: one line each 42 km every 6.4 s
Resolution 10 km at s.s.p.
Coverage / Cycle Near-global coverage twice/day
Mass 35 kg Power 24 W Data Rate 2.88 kbps

 

Providing Agency NOAA
Instrument Maturity Flown on operational programme
Utilization Period: 2005-08-30 to ≥2024
Last update: 2017-03-29
Detailed characteristics

Wavelength

Wave number

Bandwidth

SNR @ specified input(for expected maximum temperature)

SNR @ specified input(for reference 300 K)

14.95 µm

669 cm-1

3 cm-1

40 @ 118 mW m-2 sr-1 cm

50 @ 150 mW m-2 sr-1 cm

14.71 µm

680 cm-1

10 cm-1

143 @ 96 mW m-2 sr-1 cm

223 @ 149 mW m-2 sr-1 cm

14.49 µm

690 cm-1

12 cm-1

127 @ 63 mW m-2 sr-1 cm

297 @ 148 mW m-2 sr-1 cm

14.22 µm

703 cm-1

16 cm-1

238 @ 63 mW m-2 sr-1 cm

475 @ 147 mW m-2 sr-1 cm

13.97 µm

716 cm-1

16 cm-1

436 @ 91 mW m-2 sr-1 cm

694 @ 146 mW m-2 sr-1 cm

13.64 µm

733 cm-1

16 cm-1

468 @ 111 mW m-2 sr-1 cm

599 @ 144 mW m-2 sr-1 cm

13.35 µm

749 cm-1

16 cm-1

624 @ 125 mW m-2 sr-1 cm

709 @ 142 mW m-2 sr-1 cm

12.47 µm

802 cm-1

16 cm-1

1751 @ 175 mW m-2 sr-1 cm

894 @ 134 mW m-2 sr-1 cm

11.11 µm

900 cm-1

35 cm-1

360 @ 54 mW m-2 sr-1 cm

1175 @ 117 mW m-2 sr-1 cm

9.71 µm

1030 cm-1

25 cm-1

894 @ 134 mW m-2 sr-1 cm

625 @ 94 mW m-2 sr-1 cm

7.33 µm

1364 cm-1

40 cm-1

120 @ 24 mW m-2 sr-1 cm

218 @ 43 mW m-2 sr-1 cm

6.52 µm

1534 cm-1

55 cm-1

38 @ 7.5 mW m-2 sr-1 cm

138 @ 27 mW m-2 sr-1 cm

4.57 µm

2188 cm-1

23 cm-1

577 @ 3.5 mW m-2 sr-1 cm

577 @ 3.5 mW m-2 sr-1 cm

4.52 µm

2210 cm-1

23 cm-1

740 @ 2.2 mW m-2 sr-1 cm

1070 @ 3.2 mW m-2 sr-1 cm

4.47 µm

2237 cm-1

23 cm-1

342 @ 1.4 mW m-2 sr-1 cm

735 @ 2.9 mW m-2 sr-1 cm

4.45 µm

2247 cm-1

23 cm-1

215 @ 0.86 mW m-2 sr-1 cm

710 @ 2.8 mW m-2 sr-1 cm

4.13 µm

2420 cm-1

28 cm-1

2208 @ 4.4 mW m-2 sr-1 cm

770 @ 1.5 mW m-2 sr-1 cm

4.00 µm

2500 cm-1

35 cm-1

2260 @ 4.5 mW m-2 sr-1 cm

545 @ 1.1 mW m-2 sr-1 cm

3.76 µm

2660 cm-1

100 cm-1

2900 @ 2.9 mW m-2 sr-1 cm

650 @ 0.65 mW m-2 sr-1 cm

0.69 µm

N/A

0.05 µm

1000 @ 100 % albedo

1000 @ 100 % albedo

Satellites this instrument is flying on

Note: a red tag indicates satellites no longer operational, a green tag indicates operational satellites, a blue tag indicates future satellites

Instrument classification
  • Earth observation instrument
  • Passive optical radiometer or spectrometer
  • Cross-nadir infrared sounder, possibly including VIS channels
Mission objectives
Primary mission objectives
  • Atmospheric temperature
  • Integrated Water Vapour (IWV)
  • Specific humidity
Secondary mission objectives
  • Sea surface temperature
Opportunity objectives
  • Cloud cover
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Tentative Evaluation of Measurements

The following list indicates which measurements can typically be retrieved from this category of instrument. To see a full Gap Analysis by Variable, click on the respective variable.

Note: table can be sorted by clicking on the column headers
VariableRelevance for measuring this variableOperational limitationsExplanation
Atmospheric temperature3 - highCloud sensitive.. Coarse vertical resolution.Many MWIR and TIR channels in the 4.3 and 15 micrometer bands
Cloud cover4 - fairDiscontinuous coverage.MWIR and TIR channels
Cloud top height2 - very highDiscontinuous coverage.TIR channels in window and water vapour band (for emissivity) for temperature; and in CO2 band for atmospheric column above cloud top
Cloud top temperature2 - very highDiscontinuous coverage.TIR channels in window and water vapour band (for emissivity)
Cloud type4 - fairDiscontinuous coverage.MWIR and TIR channels
Downward long-wave irradiance at Earth surface3 - highCloud sensitive.. Highly indirect.MWIR and TIR channels including water vapour and CO2 bands
Land surface temperature3 - highCloud sensitive.. Coarse spatial resolution.MWIR and TIR channels in windows and absorption bands for atmospheric corrections
O3 Total Column5 - marginalCloud sensitive.TIR channel(s). Ozone lines in band around 9.7 micrometers
Sea surface temperature2 - very highCloud sensitive.MWIR and TIR window channels (cloud impact reduction, water vapour correction)
Specific humidity3 - highCloud sensitive.. Very coarse vertical resolution.. Middle troposphere only.TIR channels in the water vapour band around 6.3 micrometers
Integrated Water Vapour (IWV)3 - highCloud sensitive.. Inaccurate in high troposphere.TIR channels around 6.3 micrometers and in the 11 micrometers split window
Upward long-wave irradiance at TOA4 - fairSpectral interpolation needed.MWIR and TIR channels in windows around 3.7 and 11 micrometers, and in water vapour and CO2 bands around 4,3, 6.3 and 15 micrometers
Upward long-wave irradiance at Earth surface3 - highCloud sensitive.. Highly indirect.MWIR and TIR channels in windows around 3.7 and 11 micrometers, and in water vapour and CO2 bands around 4,3, 6.3 and 15 micrometers