from the Amazing-Grace dept.
The Gravity Recovery and Climate Experiment (GRACE) mission has come to an end after more than 15 years in Earth orbit. The twin satellites chronicled the changes of the Earth's water, ice, and land since the spacecraft were launched from the Plesetsk Cosmodrome on March 17, 2002, on a mission that was originally only slated to last some five years. More than a decade after that, GRACE was still beaming data back to Earth when a technical issued forced mission planners to close out the program.
Similar in some aspects to other missions launched, GRACE made precise measurements via the two spacecraft – GRACE-1 and GRACE-2 – that comprised the mission. For GRACE's overall scientific objectives to be achieved the two satellites both had to be fully functional. However, this past September (2017), GRACE-2 encountered a battery issue that made it clear by mid-October that the battery would not allow scientists to operate its science instruments and telemetry transmitter. It was decided to decommission GRACE-2 and, in so doing, end GRACE's scientific mission.
[...] GRACE helped detail how our home world's changing seasons move water, ice, and even land (as a result of surface water mass changes) across the planet's surface, providing researchers with a better understanding of what drives the motion of these substances. Earth's climate, earthquakes, and our own activities all play their part in shaping the face of our world and GRACE provided insights into the dynamics of this change.
GRACE was able to detect changes in Earth's gravitational field that is related to our planet's mass which is, perhaps unsurprisingly, impacted by the redistribution of water across the globe. The spacecraft judged the distance between its two components using a microwave ranging system which, according to NASA, had the ability to judge that distance "...within a fraction of the diameter of a human hair over 137 miles (220 kilometers)."
The "Follow-On" mission is scheduled to launch within the next few months. GRACE-FO will have a laser ranging system with 20 times the sensitivity of GRACE.
Two similar missions: the ESA's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE), and Gravity Recovery and Interior Laboratory (GRAIL) which mapped the Moon.
The Lunar and Planetary Science Conference announced on 2015-03-16 that a 198 km wide crater has been found on the moon using the GRAIL spacecraft that uses gravitational field mapping. This enabled the discovery of craters below the surface. It's been named the Earhart crater. Nice gravitational photos can be found in the links.
"Japan's space agency said it had discovered an enormous cave beneath the lunar surface that could be turned into an exploration base for astronauts."
"The chasm, 50km (31 miles) long and 100 metres wide, appears to be structurally sound and its rocks may contain ice or water deposits that could be turned into fuel, according to data sent back by the orbiter, nicknamed Kaguya after the moon princess in a Japanese fairytale."
According to a science news article by UPI (United Press International):
In a new study published this week in the journal Geophysical Research Letters, scientists confirmed the presence of a large lava tube among the Marius Hills, a series of lunar lava domes.
The open lava tube could serve like a giant bunker, providing shelter from the harsh conditions on the moon's surface. In their study, scientists argue lava tubes offer ideal protection from extreme temperature swings, radiation and meteorite impacts.
Lava tubes form when the outer edges of a lava flow harden into crust and the remaining lava drains away, leaving an empty cylinder.
"It's important to know where and how big lunar lava tubes are if we're ever going to construct a lunar base," Junichi Haruyama, a senior researcher at JAXA, Japan's space agency, said in a news release. "But knowing these things is also important for basic science. We might get new types of rock samples, heat flow data and lunar quake observation data."
The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission team plans to switch to a backup system in the Microwave Instrument (MWI) on one of the twin spacecraft this month. Following the switch-over, GRACE-FO is expected to quickly resume science data collection.
A month after launching this past May, GRACE-FO produced its first preliminary gravity field map. The mission has not acquired science data since mid-July due to an anomaly with a component of the Microwave Instrument on one of the GRACE-FO spacecraft. The mission team is completing its investigation into the cause of the anomaly.
The primary science objective of GRACE-FO -- like its predecessor GRACE, which operated from 2002 to 2017 -- is to track how water is redistributed on Earth, by producing highly accurate, monthly gravity field maps. Measurements of changes in Earth's gravity field provide measurements of mass change and enable unique insights into Earth's changing climate, Earth system processes like droughts and sea level changes, and the impacts of human activities on water resources.