Unique antenna’s radar gives Nasa a headache

Nasa engineers are wrestling with a $915m (£586m) satellite that began to malfunction just six months after launch.

The Soil Moisture Active Passive (Smap) spacecraft was launched on 31 January into a polar orbit with an altitude of 685km. It is designed to measure the water content of the top 5cm of soil everywhere on Earth.

1823The Smap spacecraft’s malfunctioning radar is resisting rescue attempts.

This topsoil is where our food grows, and Smap was going to map changes in this layer over a three-year period. However, on 7 July the spacecraft’s radar abruptly stopped working.

The radar’s 6-metre antenna is unique, having been packed for launch and then deployed in space. The radar is one of the mission’s two main science instruments. Representing the “active” part, it uses a high-power amplifier to bounce radar waves off Earth’s surface.

This data is then combined with that from the “passive” instrument, a radiometer that measures the naturally emitted microwaves from the ground.

A team of engineers at Nasa’s Jet Propulsion Laboratory in Pasadena, California, believe that the fault can be traced to a low-voltage power unit. However, several attempts to bring the radar back online have been unsuccessful, and the team are continuing their analysis. The next restoration attempt could be made towards the end of August.

If the radar is unrecoverable, the radiometer data could be used in conjunction with existing data from the European Space Agency’s Soil Moisture and Ocean Salinity (Smos) satellite to achieve some of the mission’s goals.

Source: www.theguardian.com