The Ganymede laser altimeter (GALA): key objectives, instrument design, and performance

DOI: 
10.1007/s12567-019-00282-8
Publication date: 
01/10/2019
Main author: 
Hussmann, Hauke
IAA authors: 
Lara, Luisa M.;Castro-Marin, Jose M.;Herranz de la Revilla, Miguel;Jiménez-Ortega, Jaime;Martínez-Navajas, Ignacio;Rodrigo, Julio
Authors: 
Hussmann, Hauke;Lingenauber, Kay;Kallenbach, Reinald;Enya, Keigo;Thomas, Nicolas;Lara, Luisa M.;Althaus, Christian;Araki, Hiroshi;Behnke, Thomas;Castro-Marin, Jose M.;Eisenmenger, Henri;Gerber, Thomas;Herranz de la Revilla, Miguel;Hüttig, Christian;Ishibashi, Ko;Jiménez-Ortega, Jaime;Kimura, Jun;Kobayashi, Masanori;Lötzke, Horst-Georg;Lichopoj, Alexander;Lüdicke, Fabian;Martínez-Navajas, Ignacio;Michaelis, Harald;Namiki, Noriyuki;Noda, Hirotomo;Oberst, Jürgen;Oshigami, Shoko;Rodríguez García, Juan Pablo;Rodrigo, Julio;Rösner, Kerstin;Stark, Alexander;Steinbrügge, Gregor;Thabaut, Pascal;del Togno, Simone;Touhara, Kazuyuki;Villamil, Sebastian;Wendler, Belinda;Wickhusen, Kai;Willner, Konrad
Journal: 
CEAS Space Journal
Refereed: 
Yes
Publication type: 
Article
Pages: 
381-390
Abstract: 
The Ganymede Laser Altimeter (GALA) is one of the ten scientific instruments selected for the Jupiter Icy Moons Explorer (JUICE) mission currently implemented under responsibility of the European Space Agency (ESA). JUICE is scheduled for launch in mid 2022; arrival at Jupiter will be by end of 2029 with the nominal science mission—including close flybys at Ganymede, Europa, and Callisto and a Ganymede orbit phase—ending by mid 2033. GALA's main objective is to obtain topographic data of the icy satellites of Jupiter: Europa, Ganymede, and Callisto. By measuring the diurnal tidal deformation of Ganymede, which crucially depends on the decoupling of the surface ice layer from the deep interior by a liquid water ocean, GALA will obtain evidence for (or against) a subsurface ocean in a 500 km orbit around the satellite and will provide constraints on Ganymede's ice shell thickness. In combination with other instruments, it will characterize the morphology of surface units on Ganymede, Europa, and Callisto providing not only topography but also surface roughness and albedo (at 1064 nm) measurements. GALA is a single-beam laser altimeter operating with up to 50 Hz (nominal 30 Hz) shot frequency at a wavelength of 1064 nm and pulse lengths of 5.5± 2.5 ns using a Nd:YAG laser. The return pulse is detected by an Avalanche Photo Diode (APD) with 100 MHz bandwidth and is digitized at a sampling rate of 200 MHz providing range measurements with a subsample resolution of 0.1 m and surface roughness measurements from pulse-shape analysis on the scale of the footprint size of about 50 m at 500 km altitude. The instrument is developed in collaboration of institutes and industry from Germany, Japan, Switzerland, and Spain. <P />
Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074658274&doi=10.1007%2fs12567-019-00282-8&partnerID=40&md5=0fc36d9bd64cf6d4d928e3a7e74f2a98
ADS Bibcode: 
2019CEAS...11..381H
Keywords: 
Laser Altimetry;Solar System;Satellites of Jupiter;Ganymede;JUICE mission;GALA