Microsatellites aim to fill weather-data gap

The COSMIC radio-sounding satellites are ageing but may set the stage for a commercial system.

Credit: OSC/UCAR

Some orbiting satellites look up at the stars and most point down towards Earth but the satellites of the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) look sideways, across the curving horizon.

There, dozens of satellites that are part of the Global Positioning System (GPS) pop in and out of view at the edge of the planet. By tracking their radio signals, COSMIC can provide atmospheric data that enhance weather forecasts and climate models.

But the fleet, launched six years ago at a cost of US$100 million, is nearing the end of its life, with one satellite of the original six already defunct.

At a three-day workshop last month at the University Corporation for Atmospheric Research (UCAR) in Boulder, Colorado, researchers hailed the US–Taiwanese COSMIC as a pioneer and discussed plans for a commercial successor: a network of 24 micro­satellites dubbed the Community Initiative for Cellular Earth Remote Observation (CICERO).

Researchers say that the programme could help to address a gap in atmospheric data as the United States struggles to meet a 2016 launch date for the first spacecraft in its expensive Joint Polar Satellite System (JPSS).

The radio-sounding technique that both COSMIC and CICERO use is a “disruptive technology”, says Rick Anthes, a COSMIC scientist and former president of UCAR. “The impact is huge — especially the impact for the cost.”

GPS radio signals, picked up by Earth-bound receivers in everything from mobile phones to missiles, yield precise position information. But COSMIC puts them to a different use.

The signals travel at a known rate, but skimming through the planet’s atmosphere and back out to space bends the signals and delays them; COSMIC uses the length of the delay to measure the atmospheric density, which can provide information on changing characteristics such as temperature and moisture levels (see ‘Bending for data’). It makes many hundreds of these radio-occultation measurements each day.