For the last three years the European deep-space optical communications program had been based on the Asteroid Impact Missions (AIM), a rendezvous mission with the double-Asteroid Didymos. Unfortunately, the AIM mission was not approved by ESA council and efforts are now concentrated on the implementation of a Deep-space Optical Communication System (DOCS) in a Space Weather (SWE) mission to libration orbit L5 within the frame of ESA’s Space Situational Awareness (SSA) program. DOCS is an in-orbit technology demonstration that also serves a scientific objective, namely the transfer of high-resolution solar imagery. The characteristics of the SWE L5 mission allow significant simplifications in deep-space optical communication terminal design, because the equidistant triangular orbital geometry between the sun, the Earth and L5 (all three distances are 1 AU = 150 Mio km) ensures that the sun is always separated by 60 degrees from both, the space and the ground terminal. This allows for very efficient solar stray-light shielding and thermal management. It also minimizes the pointing requirements of the DOCS space terminal; a coarse pointing mechanism is not required, nor is a point ahead mechanism. The SSA SWE L5 mission Phase A, Phase B1 and B2 studies will be conducted 2017 - 2019. DOCS aims to demonstrate a data rate of 10 Mbps over 150 Mio km to a 4 m optical ground station. The paper will give an overview of deep-space optical communication technology developments and present the design and performance of the Deep-space Optical Communication System (DOCS).
This paper addresses the interferometric measurements performed on PLANCK Secondary reflector-Flight Model (SRFM) during the cryo-optical test at the Centre Spatial de Liege in Belgium. It was requested to measure the changes of the surface figure error (SFE) with respect to the best ellipsoid, between 293 K and 50 K, with a 1 μm RMS accuracy. To achieve this, Infra Red interferometry has been selected and a dedicated thermo mechanical set-up has been constructed. One emphasizes on the solutions adopted to cope with high surface slopes appearing at cryogenic temperature. Indeed, detector resolution has been exploited to resolve high density fringes at the expense of the aperture. A stitching procedure has been implemented to reconstruct the full aperture measurement with success. Test results are presented.