The GRACE-FO mission has mapped deviation in Earth’s surface mass and spatial variations in the rate of sea-level rise between 1993 and 2018 using altimetric and gravimetric analysis.

  1. The GRACE missions measure variations in gravity over Earth’s surface, producing a new map of the gravity field every 30 days.
  2. GRACE-FO will continue the work of tracking Earth’s water movement to monitor changes in underground water storage, the amount of water in large lakes and rivers, soil moisture, ice sheets and glaciers, and sea level caused by the addition of water to the ocean.
  3. These discoveries provide a unique view of Earth’s climate and have far-reaching benefits to society and the world’s population.

GRACE-FO Mission:

  • The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission launched in 2018 is a partnership between NASA and the German Research Centre for Geosciences (GFZ).
  • It is a successor to the original GRACE mission, which orbited Earth from 2002-2017.
  • It carries on the extremely successful work of its predecessor while testing a new technology designed to dramatically improve the already remarkable precision of its measurement system.

How did NASA measure this?

(1) Altimetric Study

  • Altimetry missions are used to know the ocean surface topography — the shape and height of the ocean’s peaks and valleys.
  • Radar altimeters continually send out pulses of radio waves (microwaves) that bounce off the surface of the ocean and reflect back toward the satellite.
  • The instrument calculates the time it takes for the signal to return, while also tracking the precise location of the satellite in space. From this, scientists can derive the height of the sea surface directly underneath the satellite.

(2) Gravimetric Study :

  • Gravimetry is a process of using ice’s gravitational pull on a pair of satellites. It helps estimate ice loss and its contribution to sea-level rise.
  • The twin satellites in each mission detect subtle shifts in Earth’s gravity field.
  • The strength of gravitational forces is determined by mass, so changes in Earth’s gravity field indicate a change or redistribution in mass.