Earth
Science Reference Handbook
[ Missions: Aura ] 107
OMI
Ozone Monitoring Instrument
OMI Background
OMI is an advanced hyperspec-
tral imaging spectrometer with
a 114º field of view. Its nadir
spatial resolution ranges from
13 km × 24 km to 13 km × 48 km
for ozone profiles. It has a 2600–km
viewing swath that runs perpendicu-
lar to the orbit track so that OMI’s
swaths almost touch at the equator,
enabling complete coverage of the
sunlit portion of the atmosphere each day. OMI contains two spec-
trometers: one measures the UV in the wavelength range of 270–380
nm, while the other measures the visible in the range of 350–500
nm. Both spectrometers have a bandpass of about 0.5 nm with
spectral sampling over the range 0.15–0.32 nm/pixel, depending on
wavelength. OMI uses a charge–coupled device (CCD) solid–state
detector array to provide extended spectral coverage for each pixel
across the measurement swath.
OMI is Aura’s primary instrument for tracking global ozone
change and continues the high–quality column–ozone record be-
gun in 1970 by the Nimbus–4 BUV. Because OMI has a broader
wavelength range and better spectral resolution than previous
instruments, i.e., OMI’s horizontal resolution is about four times
greater than that of TOMS, OMI can also measure column amounts
of trace gases important to ozone chemistry and air quality. The
data from OMI can be used to map aerosols and estimate ultraviolet
radiation reaching Earth’s surface.
OMI was built by Dutch Space and TNO TPD in the Neth-
erlands in co–operation with Finnish VTT and Patria Advanced
Solutions Ltd. KNMI (Royal Netherlands Meteorological Institute)
is the Principal Investigator Institute. Overall responsibility for
the OMI mission lies with the Netherlands Agency for Aerospace
Programmes (NIVR), with the participation of the Finnish Meteo-
rological Institute (FMI).
OMI Contributions to Science Questions
Is the Stratospheric Ozone Layer Recovering?
OMI continues the 25–year satellite ozone record of SBUV and
TOMS, mapping global ozone change (column amounts and pro-
files); data returned is used to support congressionally mandated
and international ozone assessments. OMI has a broader wavelength
range and better spectral resolution than previous ozone measur-
ing instruments, and this should help scientists resolve differences
among satellite and ground–based ozone measurements. OMI
also measures the atmospheric column amounts of radicals such
as nitrogen dioxide (NO
2
), bromine oxide (BrO), and chlorine
dioxide (OClO).
Key OMI Facts
Heritage: Total Ozone Mapping
Spectrometer (TOMS), Solar Backscatter
Ultraviolet (SBUV), Global Ozone
Monitoring Experiment (GOME), Scanning
Imaging Absorption Spectrometer for
Atmospheric Chartography (SCIAMACHY),
Global Ozone Monitoring by Occultation of
Stars (GOMOS)
Instrument Type: Wide–field imaging
spectroradiometer
Scan Type: Non–scanning
Spectral Bands:
Visible: 350–500 nm
UV–1: 270–314 nm
UV–2: 306–380 nm
Spectral Resolution: 0.63–0.42 nm full
width at half maximum (FWHM)
Spectral Sampling: 2–3 for FWHM
Dimensions: 50 cm × 40 cm × 35 cm
Mass: 46.06 kg
Power: 56 W (operational average)
Duty Cycle: 60 minutes on daylight side
Data Rate: 0.77 Mbps (average)
Telescope FOV: 114
o
(2600 km on ground)
IFOV: 3 km, binned to 13 km × 24 km
Detector: CCD, 780 × 576 (spectral ×
spatial) pixels
Pointing (arcsec)
(platform+instrument, pitch:roll:yaw, 3σ):
Accuracy: 275:275:275
Knowledge: 28:28:28
Stability (6 s): 28:28:28
Calibration: A white–light source is
included onboard, as well as Light–
Emitting Diodes (LEDs), a multi–surface
solar–calibration diffuser, and a scrambler
that scrambles the polarization from the
back–scattered radiation.
Contributors
Industry Design and Assembly: Dutch
Space (Netherlands), TNO (Netherlands),
VTT (Finland), and Patria Advanced
Solutions Ltd. (Finland)
Space Agencies and Funding: NIVR
(Netherlands), with participation of FMI
(Finland)
Responsible Centers: KNMI (Netherlands)
and FMI (Finland)
Earth Science Reference Handbook
108 [ Missions: Aura ]
Key TES Facts
Heritage: Atmospheric Trace Molecule
Spectroscopy experiment (ATMOS),
Stratospheric CRyogenic Infrared
Balloon Experiment (SCRIBE), Airborne
Emission Spectrometer (AES)
Instrument Type: Infrared–Imaging
Fourier Transform Spectrometer
Scan Type: Both limb and nadir
scanning; fully targetable
Spectral Range: 3.2–15.4 µm, with four
single–line arrays optimized for different
spectral regions
Maximum Sampling Time: 16 s w/signal–
to–noise ratio of up to 200:1
Swath: 5.3 km × 8.5 km
Spatial Resolution: 0.53 km × 5.3 km
Dimensions:
Stowed: 140 cm × 130 cm × 135 cm
Deployed: 304 cm × 130 cm × 135 cm
Mass: 385 kg
Thermal Control: 2 pulse–tube coolers,
heater, radiators
Thermal Operating Range: 0–30º C
Power: 334 W
Duty Cycle: Variable
Data Rate: 6.2 Mbps (peak); 4.9 Mbps
(average)
FOV: +45º to –72º along–track, ±45º
cross–track
Instrument IFOV: 12 × 7.5 mrad
Pointing Requirements
(platform+instrument, 3σ):
Control: 156 arcsec (pitch)
Knowledge: 124 arcsec
Stability: 156 arcsec (over 50 s)
Calibration: On–board 340–K blackbody;
cold space.
Responsible Center: NASA JPL
What are the Processes Controlling Air Quality?
Tropospheric ozone, nitrogen dioxide, sulfur dioxide, and aerosols
are four of the U.S. Environmental Protection Agency’s six criteria
pollutants. OMI maps tropospheric column totals of sulfur diox-
ide and aerosols. Scientists can take advantage of the synergistic
nature of the Aura instruments and combine measurements from
OMI, MLS, and HIRDLS, to produce maps of tropospheric ozone
and nitrogen dioxide. In addition, OMI also measures the tropo-
spheric ozone precursor formaldehyde. Scientists plan to use OMI
measurements of ozone and cloud cover to derive the amount of
ultraviolet (UV) radiation reaching Earth’s surface. The National
Weather Service will use OMI data to forecast high UV index days
for public health awareness.
How is Earth’s Climate Changing?
OMI tracks ozone, dust, smoke, biomass burning, and industrial
aerosols in the troposphere. OMI’s UV measurements allow sci-
entists to better distinguish reflecting and absorbing aerosols, an-
other important step forward in helping scientists more accurately
represent aerosols in climate models.
OMI Principal Investigators
Pieternel Levelt, Royal Netherlands Meteorological Institute
(KNMI) (Netherlands)
Johanna Tamminen, Finnish Meteorological Institute (Finland)
Ernest Hilsenrath, NASA Goddard Space Flight Center (U.S.)
OMI URL
www.knmi.nl/omi
TES
Tropospheric Emission Spectrometer
TES Background
TES is a high–resolution infrared–imaging Fourier Transform
Spectrometer with spectral coverage of 3.2–15.4 µm at a spectral
resolution of 0.025/cm. The instrument can provide information
on essentially almost all radiatively active gases in Earth’s lower
atmosphere, both night and day. TES makes both limb and nadir
observations. In the limb mode, TES has a height resolution of
2.3 km, with coverage from the surface to 34 km altitude. In the
nadir mode, TES has a spatial resolution of 5.3 km × 8.5 km. The
instrument can be pointed to any target within 45° of the local verti-
cal. TES uses the same cryogenic refrigeration system described
under HIRDLS to allow for detection of weak infrared radiation
from Earth’s atmosphere.