XMM Radiation Environment Workshop

Held 29 Nov - 1 Dec 2000 at XMM-Newton Science Operations Centre, Villafrana Tracking Station, Madrid


Attendees

ESTEC : E Daly, C Erd, H Evans, P Gondoin, F Jansen, D Lumb, R Much,

VILSPA : B Altieri, M Bremmer, M Casale, J Clavel, M Ehle, C Gabriel, F Giannini, M Guainazzi, J Lin, M Santos, N Schartel, M Smith, D Texier, A Tiengo

Leicester : A Abbey, P Bennie, G Griffiths, D Smith

SRON Utrecht : J-W den Herder

MPE Garching : U Briel, K Dennerl, G Hartner, E Pfeffermann, W Pietsch,

AIT Tubingen: E Kendziorra

MPI-HLL : N Meidinger, L Struder

CNR Milano : S Molendi, G Villa

CEN SACLAY : P Ferrando

DERA : F Lei

CHANDRA : P Plucinsky, R Cameron, M Bautz


The following collection of presentation summaries has been partly collated from electronic source material, and partly from scanned copies of original viewgraphs. The quality of the latter are particularly variable. We apologise in advance in these cases. If you have a particular question it is suggested you contact the author directly. A brief description of the content of each talk is given below, with links to the material presented.

D Lumb
introduced the meeting setting out the major items of study which he felt needed addressing

Agenda


E Daly
summarised the modelling made pre-launch for the understanding of low energy proton damage, which had been triggered by the early in-orbit damage to the CHANDRA ACIS detectors.

WMA Study Environmental models were shown. Specifically historical data from IMP-8 had been used to scale the expected soft proton fluence that might lead to an XMM-Newton efficiency of operations. The short-lived Equator-S mission had provided data to show magnetospheric fluxes of protons could vary 2.5 orders of magnitude. Magnetospheric scientists describe the bursts of protons as coming from magnetic reconnection events: "bursty reconnection"


H Evans
reviewed the data obtained from the XMM-Newton Radiation monitor. Displays of data make sense in nominal geomagnetic B/L cordinates, but this misses the dynamism of the magnetic field. Total dose for the two major solar proton flare events were thought to be 5krads (Si in 4mm AL)

XMM Orbit Environment


F Lei
reviewed the results of a previous ESA-sponsored study into predicted background for XMM. The resulting fluorescent and Compton background on the input of a primary cosmic ray background had been assessed. This is some 2 orders magnitude lower than the measured background - the conclusion was that the study had taken as baseline that the CCD detetcors would be much more efficient at rejecting the prompt particles.

DERA presentation


J-W Den Herder
described background and damage aspects of RGS. There is no simple background determination for RGS. They see clear signs of a vignetting of soft proton background. Instrument degradation was discussed in terms of system peak changes, hot pixels, CTI and contamination degradation. CTI damage is currently seen as no problem for 10 years mission. Contamination as evidenced by the change in calibration sources relative intensity is more likely due to contamination on the Curium source itself.

RGS contribution


K Dennerl
described the monitoring methods of assessing PN CTI. Measurements indicate minimal degradation to date, but this is masked by gain changes due to drifts in platform temperature.

PN CTI


N Meidinger
Recalled the pre-launch proton testing campaigns for EPIC PN. No major degradation expected after a mission dose, and tests were conducted up to 10MeV equivalent dose of 6.5e9/sq cm. In orbit a barely detectable change in Mn K peak height of order 3 ADU was found. Converting to CTI delta of 4 e-13 /p/sq cm this implies an equivalent dose of order 6e7 p/sq cm (1/10 mission dose). This implies we are on course to meet expectations. Reviewed changes in bad pixel tables and offset maps

PN Proton damage


L Struder
The set of newly observed bad pixels were apparently switched on at a sudden event (step change), whose time was traced down using the HKD. Hypothesised that the instantaneous generation of sets of bad pixels may have been due to ingress of a micrometorite into the telescope volume, resulting in localised silicon melting

Micrometeorite damage?


E Kendziorra
Discussed methods for using the PN discarded line counter to estimate the soft proton flux. The alternate methods which might be used in SW and TIMING modes was addressed.

Correlating PN count rates


P Bennie
Discussed the CTI monitoring in EPIC MOS. A small change with time is seen. the slope of change altered around July, and this was attributed to changes in protecting against soft proton events. Steps in CTI data were seen at the solar flares in July and September.

MOS CTI & bad pixels Increases in number of bad pixels were described. The concern centred around MOS2. There was a step change in number around rev 107/108. This is reminiscent of the step change in PN described previously. However the "event" occurred between science revolutions, near perigee, and if attributed to micrometeorite damage would be bizarre as except for a period of <2minutes the filterwheels had been closed the whole period.


A Abbey
Showed how the presence of new bad pixels was manifested on the Leicester summary processing system. Briefly reviewed how the bad pixels were repeatedly annealed on HST, and posed whether this was a suitable approach for EPIC. Also questioned if that the current though small level of CTI degradation, plus these bad pixels, already give a strong motivation to reduce the MOS operating temperature.

Link to A Abbey presentation


P Ferrando
Discussed the analysis of diagnostic images taken in flight, and how thay reveal details of the event rejection scheme efficiency, size of events etc.


S Molendi
Described analysis of excess background flare events which indicates they must be protons. Background is variable at 30% level and different components are vignetted differently. Noted the impact of high background on science areas such as clusters of galaxies and hard surveys.

S Molendi presentation Part I

S Molendi presentation Part II


D Lumb
Also described the selection of background files suitable for use in SAS with extended sources. The intensity was at variance with that of SMolendi. Showed evidence for particle events persisting over several frames, and posited might give a method for reducing background if single pixel events were also persistent

EPIC Background


P Plucinsky

Described the occurrence of the Initial CTI degradation , followed by presentations on in-orbit background measurements , and continuing monitoring of CTI changes .


R Cameron
Described the operational strategies for monitoring the Chandra radiation environment, and autonomous safing methods. Modelling of the orbit environment for predictive capability was addressed

CHANDRA Operations


F Giannini
Reviewed how the operational proceedures to keep instruments safe had evolved through the first year of the mission. Demonstrated how it is believed we should now be much more robust against ingress of soft proton events than previously, while maximising the science return.

XMM-Newton Operations


D Texier
Revealed some statistics on the efficiency of science operations, especially concentrating on the evolution of perigee passage and apparent belts' extent, and the way this is accounted for in an ad hoc manner by mission planning activities.

MOS vs RGS

MOS vs RADMON

RADMON 500cts/sec levels


A Tiengo
Described the activities at Vilspa with respect to monitoring EPIC performance, with a view to how this activity will eventually be taken over by VILSPA from the instrument teams. Discussed the measurements made during the Lockman Hole observations, where the use of different filters allowed some diagnostic of the nergy of particles detected during high background periods.

Proton Spectra and monitoring


D Lumb
reviewed conclusions and discussed future activities. Please note that action items have been appended on this note.

Conclusions


This page was cobbled together by
David Lumb
Please blame him for any errors and omissions. Contact the authors of each section for technical updates, explanations etc..

Last modified: Tue Jan 9 08:49:27 MET 2001