Speaker
Description
The instrument for SensIng electroMagnetic pulses on Cubesat (CubeSIM), currently in phase B at ONERA in the frame of the internal ONSAT-1 research project, aims to detect and measure the effects of electrostatic discharges induced by the plasma environment. The first mission envisioned to fly this instrument in SSO LEO orbit is called ChaRging On CubeSat (CROCUS). The targeted platform is a 2U cubesat from Centre Spatial Etudiant de l’Ecole Polytechnique (CSEP), currently in phase 0/A. CSEP and ONERA will be in charge of operating the spacecraft and exploiting the data, respectively. Ideally this mission would also fly the ESDEE active electron emitter under development at LATMOS. The challenge is to develop high sensitivity sensors and electronics with a limited impact for an integration on a 2U satellite (reduced power, volume and weight). The delivery of the CubeSIM flight model is expected by mid-2022.
The assessment of space environment effects is a challenge for cubesat missions because the high level expertise it requires is difficult to find within relatively small size development teams. In addition, national and international guidelines can be difficult to apply because they are intended to satellites much bigger than cubesat. These missions also lack flight feedbacks because this analysis requires information that is rarely monitored on-board. These transients have never been directly monitored on any European spacecraft and so the direct association of a particular ESD event and an operational anomaly has not been possible. ONERA, ESA and CNES are currently envisioning the development of new instruments to address questions such as how frequently ESDs occur, how robust existing protections of equipment are and how effective electrostatic charging prevention methods are.
CubeSIM is composed of a series of instruments dealing with electrostatic charging effects assessment. The FPGA-based TWIST instrument detects the occurrence of electrostatic discharges (ESD) sensed with antennae and lightweight probe sensors. SPARK regularly tests TWIST during quiet periods of time by mimicking ESDs transient waveforms deduced from ground test. MISTEEC increase the probability to get high level charging and to trigger ESDs by deploying panels made with materials with specific response to environmental plasma conditions. On the opposite, SCAPEE alleviates spacecraft charging by emitting electrons by passive field effect and tends to reduce the ESD occurrence.
We will present the experimental campaign conducted on a 2U cubesat mockup equipped with lab prototypes of TWIST and MISTEEC. The test setup has been mounted inside the JONAS vacuum plasma chamber (Onera test bench) and was electrically floating with respect to ground. The combination of a large-scale tank and floating connections avoids the electromagnetic disturbances induced by ground equipment. These conditions are strictly necessary to identify with precision the conditions leading to ESDs and to source the transient currents induced by an electron beam and a VUV source on a small satellite. About 100 ESDs have been generated and detected. We will show how these results are used to prepare the next prototypes and how, in the frame of a CNES R&D activity, they can be extrapolated to bigger platforms.
We will also quickly present the test results obtained on SCAPEE lab prototypes developed and manufactured in the frame of an ESA study. Their measured performances indicate that a few of these passive items could be sufficient to reduce drastically the negative charging of satellites undergoing severe environmental conditions, including GEO substorms. To meet the objectives of the CROCUS mission, it involves defining different CROCUS mission scenarii with separate / combined operating sequences for TWIST and SCAPEE.
