XMM Radiation Environment Workshop
Held 29 Nov - 1 Dec 2000
XMM-Newton Science Operations Centre, Villafrana Tracking Station, Madrid
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.
introduced the meeting setting out the
major items of study which he felt needed addressing
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.
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
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
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.
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.
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
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
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
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.
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
Discussed the analysis of diagnostic images taken in flight, and how thay reveal details of the event rejection scheme efficiency, size of events etc.
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
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
Described the occurrence of the Initial CTI degradation ,
followed by presentations on in-orbit background measurements ,
and continuing monitoring of CTI changes .
Described the operational strategies for monitoring the Chandra radiation
environment, and autonomous safing methods. Modelling of the orbit
environment for predictive capability was addressed
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.
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
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.
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