Satellites that monitor Earth's water are nearly out of fuel

BY LAUREL KORNFELD | PUBLISHED: 09-19-2017

Delayed launch of successor means likely gap in data crucial to climate change studies.

NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites, which have been monitoring Earth's ice and water since 2002, are running out of fuel and will likely stop functioning before their replacement is launched.

Already operating ten years beyond their lifespan, the GRACE-1 and GRACE-2 satellites, which measure tiny changes in Earth's gravity caused by the melting of polar ice and depletion of underground reservoirs, are experiencing power losses that are degrading the data they collect.
Always orbiting the Earth 220 kilometers apart, the satellites measure changes in the pull of Earth's gravity by noting the smallest increases in their distance from one another.

Massive features on Earth, such as large ice sheets, minutely increase the gravity in the regions they cover, temporarily increasing the distance between GRACE-1 and GRACE-2.

By calculating the increase in the probes' distances from one another, on board computers can determine the exact mass of the object that caused the additional movement.

GRACE-2 has burned through its fuel more quickly than expected because the battery it uses to store solar power has been malfunctioning.

Contact with the satellite was lost for four days between September 4 and 8 when an additional battery cell failed.

Although scientists feared the loss meant the mission's end, they succeeded in rebooting GRACE-2's flight software. The satellite will be in standby mode until November, when, in full sunlight, it will conduct its last collection of science data.

A successor mission, GRACE-Follow-on, which had been planned to launch before the twin satellites stop functioning, has been delayed until early 2018 due to difficulties finding a launch vehicle.

This means there will likely be a gap in data collection between the time GRACE stops functioning and the time GRACE-Follow-on resumes the collection of data.

While there are other methods of estimating mass changes in the planet's ice sheets, using data from other satellites, none is comparable for accurately monitoring mass changes in glaciers and ice caps.

There are no alternate methods available for conducting measurements of Earth's groundwater and soil moisture.

GRACE-Fo will use an experimental laser ranging interferometer that will measure the distance between the new twin satellites to an even more precise level, leading to more accurate data on the masses of Earth's ice sheets.

The GRACE satellites, a joint effort by the US and Germany, provided hydrologists and climate scientists with groundbreaking data on groundwater loss from overuse and on the effect of melting polar ice sheets on rising global sea levels.

 

 

 

Comments
Laurel Kornfeld - 5 hours ago
Delayed launch of successor means likely gap in data crucial to climate change studies.
Laurel Kornfeld - 5 hours ago
Delayed launch of successor means likely gap in data crucial to climate change studies.
Chad Young - 6 hours ago
Delayed launch of successor means likely gap in data crucial to climate change studies.
Chad Young - 6 hours ago
Delayed launch of successor means likely gap in data crucial to climate change studies.
Vicky Webb - 6 hours ago
Delayed launch of successor means likely gap in data crucial to climate change studies.
Paul Pate - 6 hours ago
Delayed launch of successor means likely gap in data crucial to climate change studies.
Laurel Kornfeld - 6 hours ago
Delayed launch of successor means likely gap in data crucial to climate change studies.