PMIRR Selected to Fly on 1998 Mars Orbiter

NASA Press Release, 21 July 1995

Douglas Isbell
Headquarters, Washington, DC                   July 21, 1995
(Phone:  202/358-1753)

RELEASE:  95-117


     NASA officials have selected an atmospheric science
instrument called the Pressure Modulator Infrared Radiometer
(PMIRR) to fly aboard the Mars Surveyor '98 orbiter, a Mars-
bound spacecraft scheduled for launch in late 1998.

     This selection helps define the mass and electrical
power requirements of the scientific payload for the mission.
The payload also will include an optical camera, which is
currently the subject of an open selection competition due to
be concluded in October.  The selection of PMIRR follows the
recommendation of an ad hoc science definition committee
chaired by Dr. Geoffrey Briggs, director of the Mars Mission
Research Center at  NASA's Ames Research Center, Mountain View, CA.

     PMIRR was chosen over a Gamma Ray Spectrometer (GRS)
instrument that would study the chemical composition of the
Martian surface.  A GRS is now tentatively planned for flight
on a NASA Mars orbiter that will be launched in 2001.

     "The PMIRR instrument will make a fundamental
contribution to our Mars program science goals," said Jurgen
Rahe, director of the Solar System Exploration Division at
NASA Headquarters.  "The GRS instrument can more easily be
accommodated on the 2001 Mars Surveyor orbiter."

     PMIRR will produce a vertical picture of the tenuous
Martian atmosphere by measuring a profile of the infrared
radiation reflected from the horizon of the planet.  These
data can be used to derive other atmospheric components such
as temperature, water vapor levels and dust content, from the
Martian surface level through altitudes as high as 50 miles.
Such information helps produce more accurate global models of
the Martian environment, a necessary precursor for future
robotic and human exploration missions.

     The principal investigator for PMIRR is Dr. Daniel
McCleese of NASA's Jet Propulsion Laboratory, Pasadena, CA.
The Mars Surveyor '98 orbiter and a separate Mars lander to
be launched in 1998 are being built for NASA by Lockheed
Martin Astronautics, Denver, CO.

     PMIRR and GRS are the two remaining instrument spares
from the Mars Observer program waiting for an opportunity to
fly again.  Mars Observer fell silent on August 21, 1993,
three days before it was to have entered orbit around Mars.
An independent investigation panel determined that the most
likely cause of this loss of communications was a high-speed
spacecraft spin that resulted from a propellant system leak.

      The other five of the seven Mars Observer science
instruments will be carried by NASA's Mars Global Surveyor
orbiter spacecraft, due for launch in November 1996.


EDITOR'S NOTE:  An artist's concept of the Mars Surveyor '98
orbiter is available for media representatives by calling the
News Branch at 202/358-1900.  
The photo number is:  Color -- 95-HC-133.