The Indian Space Research Organisation (ISRO) is soliciting proposals from the nation’s scientific community for the first in a planned series of small research satellites that will be launched as secondary payloads aboard Indian rockets.

The satellites, weighing in the neighborhood of 100 kilograms and with a scientific payload capacity of 25 kilograms, will take advantage of excess capacity anticipated on future launches, R. Sridharan, director of ISRO’s Space Science Laboratory in Trivandrum, said in a Nov. 29 telephone interview.

“Every year we have two or three launches and finding a spare capacity of 100 kilograms is not difficult,” said Sridharan, who helped hatch the project. A series of missions has been planned, with the first to be launched no sooner than two years from now, he said.

Dedicated small-satellite missions are possible now with an ” optimum cost factor,” ISRO said in a Nov. 29 announcement. Such missions could spur development of sensors, devices and computer programs “that will keep the Indian space science program at par with other international efforts.”

For the first mission, ISRO is seeking proposals in atmospheric science, potentially including studies of solar-terrestrial interaction, according to the announcement . The second mission will focus on astronomy, with proposals to be invited separately, ISRO said.

Ideally, the first of the ISRO small satellites will complement planned missions such as the U.S. Air Force’s Communications/Navigation Outage Forecasting System (C/NOFS) and Brazil’s Equatorial Atmosphere Research Satellite, the announcement said.

The C/NOFS satellite, slated for launch next year, is designed to study ionospheric phenomena in the equatorial regions that could disrupt the propagation of satellite communications and navigation signals. The Brazilian satellite, intended to study the middle and upper atmosphere, tentatively is scheduled to launch in 2007.

The atmosphere will be ISRO’s initial focus “in view of the current resurgence of interest in the field, particularly relating to the vertical coupling of lower and upper atmosphere and solar terrestrial interactive processes pertaining to space weather,” ISRO said in the announcement. The deadline for submitting the proposals is Jan. 31, 2006.

“The major focus of the proposed satellite program for tropospheric and stratospheric studies is to delineate the changes that are taking place in the atmospheric aerosol and trace gases amount in the South and South East Asian region and estimate their impact on atmospheric radiation budget, chemistry and climate,” ISRO said in the announcement.

The measurements will help identify and differentiate between natural and man-made aerosols, ISRO said.

Current ISRO research on aerosols and trace gases relies on sounding rockets , balloons and ground-based observations, and the data obtained are highly localized and region-specific.

Based in Bangalore, Killugudi S. Jayaraman holds a doctorate in nuclear physics from the University of Maryland and a master's degree in journalism from the Medill School of Journalism at Northwestern University. He was formerly science editor of the...