Abstract (Session-2): 
The Ganymede Laser Altimeter (GALA) --one of the payloads of
 ESA's Jupiter Icy Moons Explorer-- provides topographic
 measurements by time-of-flight measurements of photons 
transmitted and received by the spapcecraft at about 500 km
 altitude above the Ganymede surface. GALA uses the
 gdirect-detectionh (classical) approach of laser altimetry.
 Laser pulses are emitted at a wavelength of 1064 nm by
 using an actively Q-switched Nd:Yag laser. The pulse energy
 and pulse repetition frequency are 17 mJ and 30 Hz, respectively. 
The emission time of each pulse is measured by the detector. 
The beam is reflected from the surface and received 
at a 25 cm diameter telescope. The returning laser pulse is
 re-focused onto a silicon avalanche photodiode (APD) through
 back-end optics including a narrow bandpass interference
 filter for isolating the 1064 nm wavelength. The APD-signal
 is then amplified, sampled and fed to a digital range finder,
 providing time-of-flight, pulse-shape and intensity of the
 reflected pulse. GALA is developed in collaboration of
 institutes and industry from Germany, Japan, Switzerland 
and Spain. This talk provides a technical description of
 GALA and a summary of the instrument development status.