A few hours ago, the two GRACE-FO twin spacecraft were launched on a Falcon 9 rocket from the Vandenberg base. After about ten minutes they successfully separated from the rocket’s last stage and entered a polar orbit. Shortly thereafter they started transmitting telemetry signals. SpaceX’s mission continued with the launch of 5 satellites of the Iridium constellation.
The first stage of the Falcon 9 rocket was the one already used for the notorious Zuma mission, which was supposed to launch a spacecraft of secret nature. Officially, something went wrong due to a problem with one of the systems provided by the manufacturer that was supposed to handle the last phase of its entry into orbit. Meanwhile, SpaceX started using a new version of the first stage so there was no controlled landing while there was another experiment to recover the fairing, unfortunately again unsuccessful.
The GRACE-FO mission is a follow-up to the GRACE mission, conducted by NASA and the German space agency DLR between March 2002 and October 2017 and ended after one of the twin satellites suffered battery malfunctions. The original mission was scheduled to last 5 years but with various extensions it had a triple duration.
The GRACE-FO mission, conducted by NASA and GFZ (German Research Center for Geosciences), also has a scheduled duration of 5 years. At an altitude of 490 kilometers (305 miles), the twin satellites travel at about 7.5 km/s (16,800 mph) in a polar orbit where they will slowly move away from each other until in a few days they will be separated by about 220 kilometers (137 miles).
The two GRACE-FO satellites are an evolution of the previous satellites so they’re equipped with the same microwave system to measure their distance with extreme precision but also have a new laser ranging system. It’s a technology still in its experimental phase and potentially even more precise developed to be used in future satellites.
These systems will allow to continuously measure the distance between the two GRACE-FO satellites with extreme precision. The really tiny changes in Earth’s gravity will slightly increase and decrease that distance, allowing to map the territory under them.
These measurements will allow over time to measure changes at global levels of Earth’s seas, glaciers and even large lakes and rivers. Keeping an eye on polar ice caps and other very large ice sheets such as Greenland can provide further information on the climate changes in progress by continuing the data collection from the GRACE mission.