End-to-end numerical simulator of the Shadow Position Sensor (SPS) metrology subsystem of the PROBA-3 ESA mission

PROBA-3 - PRoject for OnBoard Autonomy is an ESA mission to be launched in 2022 where a spacecraſt is used as an external occulter (OSC-Occulter Spacecraſt), to create an artificial solar eclipse as observed by a second spacecraſt, the coronagraph (CSC-Coronagraph Spacecraſt). The two spacecraſts (SCs) will orbit around the Earth, with an highly elliptic orbit (HEO), with the perigee at 600 Km, the apogee at about 60530 Km and an eccentricity of 0.81. The orbital period is of 19.7 hours and the precise formation flight (within 1 mm) will be maintainedforabout6hours overthe apogee, in ordertoguarantee the observation ofthe solarcoronawith the required spatial resolution. The relative alignment ofthe two spacecraſts is obtained bycombining information from several subsystems. One ofthe most accurate subsystem (with accuracy >0.5 mm) is the Shadow Position Sensors (SPS), composed by eight photomultipliers installed around the entrance pupil of the CSC. The SPS will monitor the penumbra generated by the occulter spacecraſt, whose intensity will change according to the relative position ofthe two satellites. A dedicated algorithm has been developed to retrieve the displacementof the spacecraſts fromthe measurements ofthe SPS. Several tests are requiredin ordertoevaluate the robustness of the algorithm and its performances/results for different possible configurations. A soſtware simulator has been developed for this purpose. The simulator includes the possibility to generate synthetic 2-D penumbra profile maps or analyze measured profiles and run different versions ofthe retrieving algorithms, including the “on-board” version. In order to import the “as built” algorithms, the soſtware is coded using Matlab

Metrology on-board PROBA-3: The Shadow Position Sensor (SPS) subsystem

PROBA-3 is an ESA Mission whose aim is to demonstrate the in-orbit Formation Flying and attitude control capabilities of its two satellites by means of closed-loop, on-board metrology. The two small spacecraft will form a giant externally occulted coronagraph that will observe in visible polarized light the inner part of the solar corona. The SPS subsystem is composed of eight sensors that will measure, with the required sensitivity and dynamic range, the penumbra light intensity around the coronagraph instrument entrance pupil

Laboratory testbed for the calibration and the validation of the shadow position sensor subsystem of the PROBA3 ESA mission

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Metrology on-board PROBA-3: The shadow position sensors subsystem

PROBA-3 is an ESA mission aimed at the demonstration of formation flying performance of two satellites that will form a giant coronagraph in space. The first spacecraft will host a telescope imaging the solar corona in visible light, while the second, the external occulter, will produce an artificial eclipse. This instrument is named ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun). To accomplish the payload's scientific tasks, PROBA-3 will ensure sub-millimeter reciprocal positioning of its two satellites using closed-loop on-board metrology. Several metrology systems will be used and the Shadow Position Sensor (SPS) subsystem senses the penumbra around the instrument aperture and returns the 3-D displacement of the coronagraph satellite, with respect to its nominal position, by running a dedicated algorithm. In this paper, we describe how the SPS works and the choices made to accomplish the mission objectives

Status of a C-band Phased Array Feed with RFSoC digital beamformer

In this paper, we describe the design and development status of a room-temperature C-band Phased Array Feed (PAF) demonstrator, based on Radio Frequency System-on-Chip (RFSoC) for radio astronomy application, to be installed on the Sardinia Radio Telescope. The instrument is optimized to work across the 4.75-6.00 GHz radio frequency (RF) band. The project of the front-end includes a compact RF module based on an 8×8 array of linear dual-polarization antenna elements integrated with Monolithic Microwave Integrated Circuit (MMIC) Low Noise Amplifiers (LNAs). In the preliminary version of the front-end project, which considers only one linear polarization, a subset of 32 elements are connected to the LNAs, while the rest of them are terminated to 50 Ohm matched loads. A dedicated signal acquisition chain of microwave components, based on two stages of filtering and signal conditioning, permits the injection of the 32 RF signals to the two commercial back-ends based on RFSoC digital boards. Each board is equipped with 16 inputs, with 1.25 GHz instantaneous bandwidth, and performs the frequency channelization, the partial and final beamforming of at least four independent beams (the number of beams may vary depending on the observation requirements). A general description of the front-end design, the back-end hardware, firmware and software development and an optimizer for the whole system performances evaluation, is presented

Architecture of C-band Phased Array Feed with RFSoC digital beamformer

We describe the architecture of a room-temperature C-band Phased Array Feed (PAF) demonstrator based on Radio Frequency System-on-Chip (RFSoC) for radio astronomy application. The instrument operates across the 4.75-6.00 GHz RF band (C-band). The RF section includes a compact module based on an 8×8 array of dual-polarization antennas integrated with MMIC (Monolithic Microwave Integrated Circuit) Low Noise Amplifiers (LNAs). A subset of 32 elements of one of the two polarization channels of the 128 antennas are connected to the LNAs, while the rest are terminated into internal loads. Following two stages of filtering and signal conditioning, the 32 RF signals are injected in two commercial RFSoC digital boards, each accepting 16 inputs with 1.25 GHz bandwidth, that will perform the frequency channelization, the partial and final beamforming of four independent beams with 1.25 GHz instantaneous bandwidth

PROBA-3 mission and the Shadow Position Sensors: Metrology measurement concept and budget

PROBA-3 is a space mission of the European Space Agency that will test, and validate metrology and control systems for autonomous formation flying of two independent satellites. PROBA-3 will operate in a High Elliptic Orbit and when approaching the apogee at 6·104 Km, the two spacecraft will align to realize a giant externally occulted coronagraph named ASPIICS, with the telescope on one satellite and the external occulter on the other one, at inter-satellite distance of 144.3 m. The formation will be maintained over 6 hrs across the apogee transit and during this time different validation operations will be performed to confirm the effectiveness of the formation flying metrology concept, the metrology control systems and algorithms, and the spacecraft manoeuvring. The observation of the Sun's Corona in the field of view [1.08;3.0]RSun will represent the scientific tool to confirm the formation flying alignment. In this paper, we review the mission concept and we describe the Shadow Position Sensors (SPS), one of the metrological systems designed to provide high accuracy (sub-millimetre level) absolute and relative alignment measurement of the formation flying. The metrology algorithm developed to convert the SPS measurements in lateral and longitudinal movement estimation is also described and the measurement budget summarized