The Ganymede Laser Altimeter, or GALA, is one of the key scientific instruments aboard the European Space Agency’s (ESA) JUICE mission, which was launched successfully on April 14, 2023, from French Guiana. JUICE, or the Jupiter Icy Moons Explorer, is designed to study some of Jupiter’s fascinating icy moons, including Ganymede, Europa, and Callisto.
GALA’s main job is to measure the surface features of these moons with great precision. It does this by sending laser beams down to the surface and measuring how long it takes for the light to bounce back. This helps scientists map the topography of these icy bodies. One of GALA’s exciting goals is to search for a possible underground ocean beneath Ganymede’s icy shell and to observe how the ice shifts in response to gravitational pulls from Jupiter. By understanding the ice’s behaviour, GALA can provide insights into the moon’s water system.
In addition to investigating water, GALA will help describe Ganymede’s geology by capturing detailed information about its landscape on different scales. The instrument will measure factors like surface roughness and brightness across areas as small as a few tens of meters.
Ganymede is remarkable for being the largest moon in the solar system, with a unique structure that includes a mix of water ice and rock. Recent studies indicate that inside Ganymede, there is an iron-rich core surrounded by a layer of rock and a thick ice shell. Scientists believe there could be a salty ocean beneath this ice, and GALA will help determine its depth and characteristics by observing how the surface reacts to tidal forces. In addition to topographical measurements, GALA will track how Ganymede’s surface bends and flexes due to these tides. It will also work in tandem with other instruments, like cameras and radar, to provide a complete picture of the moon’s features and its geological history. Moreover, GALA will play a significant role in understanding Ganymede’s spin and rotation, which is crucial for precise mapping of the moon and its companions, Europa and Callisto. This will enhance our understanding of their movements in space and refine the reference systems for these moons.
As the first laser altimeter ever sent to an icy moon, GALA promises to greatly improve our knowledge of Ganymede, Europa, and Callisto. By combining data from GALA with other instruments onboard JUICE, scientists aim to gather remarkable insights into these intriguing worlds and their potential for hosting life.
A detailed description of the instrument together with thorough explanations of scientific objectives are neatly written in this publication to which a majority of the SCITECHSS engineers have contributed.