LIDAR altimeter conception for HERA spacecraft

Abstract

Purpose – The Asteroid Impact & Deflection Assessment (AIDA) is collaboration between the NASA DART mission and ESA Hera mission. The aim of these missions is to study the asteroid deflection through a kinetic collision. DART spacecraft will collide with Didymos-B, while ground stations monitor the orbit change. Hera spacecraft will study the post-impact scenario. The HERA spacecraft is composed by a main spacecraft and two small CubeSats. HERA will monitor the asteroid through cameras, radar, satellite-to-satellite doppler tracking, LIDAR, seismometry and gravimetry. This paper reports the first iteration on the LIDAR engineering model (HELENA). It is a TOF altimeter that provides time-tagged distances and velocity measurements. The LIDAR will be used for support near asteroid navigation and provides scientific information.

Design/methodology/approach – The HELENA design involves mainly two types of technologies: a microchip laser and low noise sensor. The synergies between these two technologies enable developing a compact instrument for range measurements of up to 14 km. The paper reports on the thermal-mechanical and radiometric simulations of the HELENA telescope. The design is subjected to vibrational, static and thermal simulations, and the obtained results show that the LIDAR telescope is compliant with the random vibration levels, the static load and the operating temperatures.

Findings (mandatory) – During the LIDAR operative life the structure is typically subjected to a diverse range of environmental conditions including vibrations, accelerations, shocks, temperature variations. Static and vibration simulations are an important tool for instrument design optimization, including the overall mass optimization. Regarding the thermal-mechanical analysis, these simulations allow to evaluate the instrument deformation for its temperature operational range. The LIDAR telescope mirrors surface deformation across operational temperature range have ben studied in particular. Two materials, aluminum and titanium, have been evaluated for the most sensitive telescope parts. Simulation results showed that titanium is the preferred material for these critical parts. These results are a first validation of Hera LIDAR telescope, and the design will be subject to further analysis with more advanced tools.

Research limitations/implications – The design approach is intended for a first iteration of the LIDAR telescope design validation. Adought future analysis using more advanced tools (e.g. ANSYS and ESATAN) can introduce some modifications, it is expected that the main features are already present in this study.

Originality/value – Low mass compact spacecraft missions to asteroids, including small landing spacecraft, are a major trend in the present mission planning for several space agencies. This approach tends to drive instrument design, pushing for miniaturization and flexibility while maintaining the performance. In particular, new compact rangefinder technologies are therefore needed for future asteroid missions. In this paper we present a very light and stiff LIDAR telescope design.