Thesis title
Mission profile for a radio interferometric observatory in lunar orbit consisting of a swarm of nanosatellites.
Composition of the jury
- Mathieu BARTHÉLÉMY (IPAG) : Rapporteur
- Benjamin GRISON (IAP - Prague) : Rapporteur
- Coralie NEINER (LIRA) :Examinatrice
- Angélica SICARD (ONERA) : Examinatrice
- Angélique RISSONS (ISAE - Supaeo) : Examinatrice
- Daniel SANTOS-COSTA (SwRI - San Antonio, Texas) : Examinateur
- Baptiste CECCONI (LIRA) : Supervisor
- Boris SEGRET (CENSUS) : Supervisor
- Louise YU (CNES) : Invited
- Laurent DUSSEAU (CSUM) : Invited
Abstract
The very low frequency radio sky (< 10 MHz) remains largely unexplored. However, many astrophysical sources and phenomena are likely to emit in this range of the electromagnetic spectrum, including planetary radio emissions and solar radio bursts. As this portion of the spectrum has never been observed with spatial resolution, it is likely that it still conceals unknown physical objects or processes. This observational gap is mainly due to the Earth’s ionosphere, which acts as a mirror for these waves and prevents detection from the ground. Furthermore, conducting high-resolution observations at these frequencies requires an instrument several kilometers in size, comparable to the wavelengths in question, and therefore necessarily deployed in space. This type of instrument can be synthesized by interferometry, using multiple spatially distributed measurement points. Thus, to explore this spectral window, the use of a space interferometer deployed on the Moon or in lunar orbit is being considered.
In this context, the NOIRE (Nanosatellites for a Radio Interferometric Observatory in Space) instrumental concept, led by the Paris Observatory, proposes to place a swarm of 50 nanosatellites into lunar orbit. An initial feasibility study was conducted in 2018, but several critical points still need to be clarified in order to formulate the system requirements necessary to begin development of the instrument. This thesis explores observation strategies for detecting planetary radio emissions, with the aim of defining a realistic mission profile for NOIRE or an equivalent mission. We show that such a concept could make a significant scientific contribution to this field of study. In this context, we have specified the sensitivity of the measurement in non-polarized beamforming mode and developed an instrumental simulator to test various observation strategies.
We also looked at the requirements related to the instrumental platform’s functions. In particular, we identified and studied an autonomous method for determining the swarm’s absolute attitude. The results of this study still need to be consolidated, but suggest that this method will ensure that the instrument is able to determine its attitude autonomously with sufficient accuracy. We have also identified requirements necessary for the successful development of these instruments, such as the need for a robust sky model to better characterize instrumental performance, as well as the need for a demonstration mission to verify the performance of the platform functions of a swarm and the ability to perform interferometric measurements. In addition, we propose methods for establishing a sky model and outline a demonstration mission.
Finally, based on scientific observation requirements, we have derived some of the main system requirements, which will guide the definition of the instrument and satellites. To conclude, we discuss the roadmap for low-frequency radio interferometers in space.
