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Last Updated on Sunday, 02 May 2010 15:02
Published on Friday, 25 February 2005 00:00


Scientists from Oxford University have a particular interest in the latest NASA mission to Mars, having played a major role in the design and construction of the main payload on board the Mars Climate Orbiter. The spacecraft, which is scheduled for launch on 10 December, will be the second in NASAs new Surveyor series of unmanned missions to the Red Planet.

'Mars Climate Orbiter is particularly significant since it will be the first mission to Mars with a substantial British component,' said Professor Fred Taylor of Oxford University's Department of Atmospheric, Oceanic and Planetary Physics.

The 44kg instrument, named PMIRR (Pressure Modulator Infrared Radiometer) represents the culmination of more than ten years of effort aimed at understanding the climate on Mars. A similar PMIRR instrument carried on a previous NASA spacecraft known as Mars Observer was lost when the spacecraft failed to respond to transmissions after it attempted to enter Mars orbit in 1993.

Many of the Mars Observer instruments were rebuilt and flown on the first Mars Surveyor but PMIRR had to wait because it was too large to be included. The new instrument has been designed and built as a collaboration between NASA's Jet Propulsion Laboratory (JPL) in California and the Department of Atmospheric, Oceanic and Planetary Physics at Oxford University. Its design is based closely upon a successful series of instruments developed by Oxford University for remote sensing the Earth's atmosphere which have flown on several NASA spacecraft since the early 1970's.

Atmospheric Science.
PMIRR's importance lies in the fact that it should provide scientists with the most complete overview of Martian weather yet obtained. From a polar orbit 400 km above Mars, PMIRR will measure the water content, dust loading and temperature of the atmosphere over the entire planet by scanning from the surface to an altitude of 80km (50 miles). The temperature measurements are particularly important because from these it is possible to learn about atmospheric circulation and winds, and study the transport of other constituents, such as water vapour and carbon dioxide, around the planet.

'We're looking to find out how the atmosphere works, how it contributes to conditions on the surface and how the climate may have changed in the past,' said Professor Taylor.

Although there are a number of similarities between the way the atmosphere behaves on Earth and Mars, the thin Martian atmosphere still holds a number of mysteries. Despite a surface pressure on Mars which is only about 1% of that on Earth, the carbon dioxide-rich atmosphere is nevertheless very active. Almost a quarter of the carbon dioxide seems to condense onto the polar ice caps during winter.

No liquid water can exist on Mars today, but water is transported in the atmosphere. By studying how the amount of water varies with altitude and latitude (distance from the equator) during the year it is hoped to obtain clues about the location of other, hidden, water reservoirs, such as subsurface permafrost.

The third extremely significant component of the atmosphere is dust, which has a considerable impact on the temperature of the atmosphere and surface. The amount varies from season to season, and occasionally global dust storms completely obscure the planet during the southern hemisphere's summer.

Starting with the 1999 Mars Polar Lander, many of the missions planned for Mars exploration over the next decade involve surface landers. While meteorological stations on the surface give extremely valuable measurements of local weather and near surface effects, the global view obtained by PMIRR will enable scientists to put this data into a planetary context.

The PMIRR data will eventually lead to more accurate global models of the Martian environment, a necessary precursor for future robotic and human exploration missions.

UK Technology.
At the heart of the PMIRR design are the pressure modulators which were developed in Oxford. These are metal cylinders about 20 cm long inside which the gas pressure is cycled about 50 times per second. PMIRR carries two modulators built by Oxford, one holding carbon dioxide and the other containing water vapour. These are the same gases which are being measured in the atmosphere.

By measuring the infrared (heat) radiation coming from the planet after it passes through the gas in the modulator, a signal is produced which is specific to the gas chosen. This is particularly useful when remote sensing Mars because the infrared radiation from the gases is mixed with radiation from the dust which always seems to be present in the atmosphere.

All of the 9 infrared detectors used in PMIRR were supplied by GEC-Marconi Infrared in Southampton. These were assembled into working optical units in Oxford and delivered to NASA/JPL for installation into the instrument. Almost all of the 52 lenses, filters and other optics used in PMIRR were supplied by Reading University Infrared Multilayer Laboratory. The only exceptions are two innovative "mesh" filters used at long infrared wavelengths which were developed and built by Queen Mary and Westfield College, London.

Notes for Editors.
Oxford University's scientific co-investigators on the Mars Climate Observer are Professor Fred Taylor, Dr. Simon Calcutt and Dr. Peter Read. The PMIRR principal investigators are Dr. Daniel McCleese of JPL and Dr. Vassili Moroz of the Space Research Institute in Moscow.

The Mars Climate Orbiter is due for launch on Dec. 10 on a Boeing Delta 2 launch vehicle from Cape Canaveral Air Station, Florida. The orbiter will arrive at the Red Planet in September 1999 and will circle Mars for a whole Martian year (about 2 Earth years) to study the atmosphere and climate. Apart from PMIRR, the only science payload on board is a 4kg colour imager comprising two tiny cameras.

The Mars Polar Lander is scheduled for launch on Jan. 3 1999. It will touch down near the planet's South Pole on Dec. 3, 1999. Riding aboard the cruise stage of the lander are two microprobes developed by NASA's New Millennium program, under the name Deep Space 2. The microprobes will be released just before atmospheric entry, and then will crash into the Martian surface near the landing site to test 10 advanced technologies and search for traces of subsurface water ice.

From 5 December, Professor Taylor and Simon Calcutt will be in the United States. Professor Taylor may be contacted by e-mail at: This email address is being protected from spambots. You need JavaScript enabled to view it.

For further information after this date contact Dr. Patrick Irwin at the Dept. of Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, Oxford University, Oxford OX1 3PU.
Tel: +44 (0)1865-272083
Fax: +44 (0)1865-272923.
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

More details of the Mars Climate Observer and Mars Polar Lander missions can be found on the Internet at the following home pages:

The UK contribution to PMIRR was funded by the Particle Physics and Astronomy Research Council (PPARC).

Peter Bond, RAS Space Science Advisor
Phone: +44 (0)1483-268672
Fax: +44 (0)1483-274047
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.