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Session 2a: Advances in On-Board Processing in Instruments and Payloads

Day 1 - Onboard processing applications
Monday, June 14, 2021
1:55 PM - 2:35 PM


Mr Alexandre Mege
Airbus Defence And Space

Hyperspectral digital backend breadboarding for microwave radiometers. 183 GHz water vapour absorption band application to SAPHIR-NG sensor

1:55 PM - 2:15 PM

Abstract Submission

In order to improve meteorological models, measurement of the atmospheric profile for water vapours is an important parameter. Space based radiometers measuring the H2O absorption band at 183 GHz can be used to measure this atmospheric profile.
SAPHIR is a radiometer instrument aboard the Megha-Tropiques spacecraft measuring the H2O absorption band at 183 GHz using 6 sub-bands from 200 to 2000 MHz. For SAPHIR-NG, a hyperspectral radiometer is considered in order to measure the absorption band using at least 256 channels over more than 10 GHz. Standard solutions based on analog filters are not viable in such a configuration, so a digital solution is required.
This CNES R&T study aims to develop a demonstrator of the digital backend of this hyperspectral radiometer based on FPGA and high speed ADC. Based on a previous study, an optimum is proposed for 256 channels over 10 GHz of bandwidth with a quantization between 4 to 6 bits at the ADC output.
The on-board digital signal processing is a filter bank followed by a power detector. A simulation of the impact of the FIR filter length and the filter window shape (rectangular, Hamming, Blackman ...) on the measurement quality (radiometric sensitivity) is performed.
The filter bank implementation in FPGA and ASIC is based on the optimised polyphase filter architecture, using a Fast Fourier Transform to efficiently channelize the signal.
In order to support the 10 GHz bandwidth, a highly parallel FFT is required. A preliminary on-board data processing feasibility analysis demonstrates that 64-samples per cycle FFT-256 working at 195.3 MHz can support 12.5 complex Gsamples/s processing for a polyphase filter with 768 taps window (i.e. 3 taps per channel). For this preliminary feasibility, 12-bit quantification is used with standard FFT scaling. Further studies will focus on optimizing the FFT scaling to reduce the required quantization.
In the frame of the demonstrator architecture definition, detailed trade-off between commercial and radiation tolerant FPGAs (Zynq Ultrascale+ RFSOC, Space Grade Kintex ultrascale, Versal AI Core and NG-ULTRA) and giga-sample ADC (EV12AQ600, ADC12DJ3200QML and ADC12DJ5200RF) are performed to select best candidates for the demonstrator.
In parallel of the FPGA based demonstrator, study of an ASIC based solution is ongoing in order to reduce the estimated 10 W consumption for the 10GHz bandwidth acquisition and processing FPGA based solution to approximately 3 W.


Ms. Laura Seoane

An autonomous control software embedded in a custom-designed electronic architecture for ExoMars’ RLS instrument to analyze samples at Mars surface

2:15 PM - 2:35 PM

Abstract Submission

ExoMars mission is ESA’s greatest commitment to reach the Red Planet in 2023 (ExoMars will take off in September 2022 and the lander will reach Mars in June 2023). ExoMars2022 aims to search for past/present life traces on Mars and to investigate the geochemical and environmental evolution of Mars. To fulfil these objectives, the Rosalind Franklin rover will be equipped with a large quantity of instruments that will allow to select and collect samples up to 2 meters in depth through a drill. Once samples are collected, the rover Sample Preparation and Distribution System will crush the samples and deliver the powdered material within the Analytical Laboratory Drawer (ALD). MicroOmega, MOMA and Raman Laser Spectrometer (RLS) are the three key scientific instruments included in ALD that will perform combined analysis to extract the most information about composition of Mars subsurface

RLS is a Raman spectrometer which provides a powerful tool for identification and characterization of minerals and biomarkers. The instrument is made up from several units: a laser for samples excitation, an internal optical head (iOH) which collects the Raman signal returned by the sample and forward to through the Spectrometer Unit where it is diffracted and projected to a CCD. All the mentioned operations are controlled by ICEU, (Instrument-Control & Excitation-Unit) a sophisticated custom electronic box designed to support an autonomous software control based on an exclusive hardware architecture composed by a FPGA (where low level drivers are hosted), a LEON2 (where Application Software (ASW) is running) and associated peripherals will be used by SW to perform assigned tasks. Therefore, RLS ASW purpose is to command and control all RLS critical elements, such as the optical head focusing mechanism, the CCD imager, and thermal control for both CCD (in order to keep it cool) and laser source (to warm it until its working temperature).

In order to obtain the maximum scientific performance at the Mars surface while optimizing the limited operation opportunities for RLS, according to the Rover Reference Surface Mission, and solving the technical difficulties intrinsic to space instrumentation, the RLS team has developed an advanced embedded software in a custom-hardware-architecture that provides an automated control of all RLS subsystems as well as post-processing capabilities to perform prompt in-situ analysis of Raman spectra.

In addition, it also includes the logic to perform automated Raman acquisitions and applying post-processing algorithm to adapt the sample acquisition parameter of every sample spot under analysis, reducing the sample fluorescence, removing undesired spikes due to Cosmic Ray impacts and by calculating the acquisition integration time. The objective of those algorithms is to maximize the Raman signal intensity of the acquired spectra, avoiding saturation level on the detector.

The RLS ASW, commands the autofocus system to guarantee that iOH is optimally focused in the accurate acquisition position over the sample. This is part of the AF algorithm function which allows effective Raman signal collection by maximizing the SNR. Finally, RLS manages communications with Rover’s MMS (Mission Management SW) implementing ‘CANopen Controller IP Core’ protocol.


Session Chairs

Daniel Lüdtke
German Aerospace Center (DLR)

Sven Wittig