The AIDA (Asteroid Impact & Deflection Assessment) is a collaboration between NASA DART mission and ESA Hera mission. The aim is to study asteroid deflection through a kinetic collision. For this mission two spacecrafts will be developed DART provided by NASA and HERA provided by ESA. DART spacecraft will collide with Didymoon, while the orbit change is monitored by ground stations. HERA spacecraft will study the post impact scenario. The HERA spacecraft is composed by the main spacecraft and two small CubeSats. HERA will study the asteroid with imaging, Radar, Satellite-to-Satellite Doppler tracking, Lidar, Seismometry and Gravimetry. We report a first iteration on the LIDAR instrument that we called HELENA (HERA LIDAR ENGINEERING MODEL ALTIMETER). HELENA is a TOF altimeter that provides time tagged distances and velocity measurements. The instrument can be used to support near asteroid navigation and provides scientific information (e.g. asteroid 3D topography, fall dawn velocity).The development of this instrument is done in the frame of an ESA activity. The LIDAR design comprises a microchip laser and a low noise sensor. The synergies between these two technologies enable the development of a compact instrument for range measurements of up to 20 km. We report the LIDAR design, namely, optics, opto-mechanics and electronics
