Space Radiation and Plasma Monitoring Workshop 2014

Calibration of Electron, Proton and Heavy-Ion Radiation Environment Data from Giove-A and Comparisons to Giove-B

13 May 2014, 14:30

25m

Newton (European Space Research and Technology Centre (ESTEC))

Presentation Radiation Monitoring Data Processing and Cross-Calibration

Speaker

Prof. Craig Underwood (University of Surrey - Surrey Space Centre)

Description

In preparation for the Galileo global navigation satellite system, the European Space Agency (ESA) commissioned two test-bed spacecraft: Giove-A, launched on 28th December 2005, and Giove-B, launched on 26th April 2008. Both spacecraft were instrumented to measure the ionising radiation environment in Medium Earth Orbit (MEO) at around 23,260 km altitude, 56o inclination. This paper reports on the results obtained from the CEDEX and MERLIN payloads on Giove-A, and methods used to provide a calibration of their data in terms of spectral fits. Comparisons are made with standard models and with the results from the SREM instrument, carried on Giove-B. The effects of cross-contamination between electron and proton data are discussed, together with the approaches taken to minimise the impact of this on modelling the environment. In general, good agreement is achieved between the different instrumental results. The ultimate aim is to be able to incorporate these calibrated flight data into standard environment model and effects tools.

Summary

The work reported on in this paper is a part of an on-going ESA study: “Exploitation of GIOVE In-Orbit Radiation Data for Environment Model and Effects Tools Update”, currently being undertaken by the Surrey Space Centre (SSC). The aim is to provide a calibration for the raw data from the Giove-A radiation environment monitoring payloads: CEDEX and MERLIN, and to compare this current standard model results and flight data obtained from the SREM instrument, flown on Giove-B.
Virtually continuous electron data have been obtained from the SURF plates inside MERLIN, and the CEDEX dose-rate-diodes over the period January 2006 to June 2012, and flux spectra have been determined for both by means of model fitting. These have been compared to each other, and cross-compared with data obtained from the SREM instrument on Giove-B since mid-2008. After processing and decontamination, the SREM and MERLIN data are found to be in good agreement. CEDEX data, responding also to Bremsstrahlung dose, are in agreement within measurement error.
Proton and heavy ion data have been similarly analysed – including a series of proton events which occurred in 2012. MERLIN particle telescope and SREM proton data were found to be contaminated with electrons, and this was dealt with by limiting the observations to higher L-shells (>8). The CEDEX particle telescope was found to be free of electron contamination, due to its 2.5mm thick copper dome. CEDEX shows very good agreement with cosmic ray models, and all three instruments show good agreement for the 2012 solar proton events.
Work is now underway to carry out a detailed comparison between the calibrated flight data and radiation belt model predictions.

Presentation materials

Slides

Calibration_of_Giove-A_ESTEC_Paper_2014.pdf