The High Resolution Dynamics Limb Sounder (HIRDLS) instrument was launched on the NASA Aura satellite in July 2004. HIRDLS is a joint project between the UK and USA, and is a mid-infrared limb emission sounder designed to measure the concentrations of trace species and aerosol, and temperature and pressure variations in the Earth's atmosphere between about 8 and 100 km. The instrument is performing correctly except for a problem with radiometric views out from the main aperture. A series of tests has led to the conclusion that optical beam is obstructed between the scan mirror and the aperture by what is believed to be a piece of Kapton film that became detached during the ascent to orbit. The paper describes measurements aimed at mapping the geometric and radiometric properties of the obstruction using different positions of the aperture door, including in some cases where the sun was made to illuminate the aperture. The aim of the work is to facilitate atmospheric observations through a small part of the aperture which remains clear.
The High Resolution Dynamics Limb Sounder (HIRDLS) instrument is scheduled for launch on the NASA AURA satellite in January 2004; it is a joint project between the UK and USA. HIRDLS is a mid-infrared limb emission sounder which will measure the concentration of trace species and aerosol, and temperature and pressure variations in the Earth's atmosphere between about 8 and 100 km altitude on a finer spatial scale than has been achieved before. This will depend upon both a high quality of instrument build, and very precise pre-launch calibration. Proto Flight Model calibration was performed in a purpose-built laboratory at Oxford University during an 13-week period in 2002. The tests were made in vacuum under cryogenic conditions close to the space environment. The measurements were divided into spectral, spatial and radiometric, with the HIRDLS pointing capability being used to control which item of test equipment was viewed. A large degree of automation was achieved, and this combined with 24-hour/7-day working enabled a large quantity of information to be obtained.
We have developed a retrieval algorithm for deriving the tropospheric CO profile and column amount from the radiances measured by the Measurements of Pollution in the troposphere instrument. The main components of the algorithm are a fast radiative transfer model, based on the GENLN2 line-by-line model, and a maximum likelihood inversion method. The retrieval a priori information is derived from the results of several aircraft in situ measurements and a 3D chemical- transport model. This paper discusses the CO retrieval algorithm with an emphasis on the analysis and characterization of the algorithm. Forward model and retrieval sensitivities, along with the a priori information used in the retrieval are discussed in terms of their orthogonal components. Examples of ensemble retrieval experiments are also included.
The Measurements of Pollution in the Troposphere (MOPJTF) instrument is a
spaceborne gas correlation radiometer designed to measure CO and CH4 in the
troposphere. This instrument has been selected to be on board of the Earth Observing
System's first platform, EOS-AM, which is scheduled for launch in 1998. A maximum
likelihood retrieval algorithm has been selected for the MOPITT CO measurement in
clear sky conditions. Performance of the algorithm has been evaluated. This paper
describes the algorithm and presents the preliminary results of numerical retrieval
The NOAA polar low earth orbit operational satellites carry HIRS2/MSU instruments and thus have thermal and microwave remote sensing capability. The measurements have been processed for retrieval of surface and atmospheric meteorological parameters using a version of the Goddard Laboratory for Atmospheres (GLA) interactive forecast-retrieval-analysis system. This interactive approach has properties that make it desirable for derivation of climate data sets, because it provides for accurate treatment of the effects of clouds on the IR radiances and elimination of some systematic errors form the retrieved quantities. The use of the microwave MSU cloud-penetrating wavelengths adds significantly to the remote sensing capabilities for the retrievals, as it allows for use of thermal data under partial cloud cover as high as 80%. Interannual differences of atmospheric temperatures derived from HIRS2/MSU on NOAA 10 show good quantitive agreement with values obtained from radiosonde reports. As part of the TOVS Pathfinder program, the retrieval system will be frozen to produce a 15 year (1979 - 1994) set of satellite-derived surface and atmospheric parameters. Data for the years 1986, 1987, and 1988 based on the current retrieval analysis are now available.