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GSFC XMM-Newton GOF Status Report #061: XMM-NEWTON NEWS #25 & #26
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_/ XMM-NEWTON NEWS #26 --- 15-Nov-2002 _/
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ESA, XMM-Newton Science Operations Centre at
Villafranca del Castillo, Satellite Tracking Station
P.O. Box - Apdo. 50727, 28080 Madrid, Spain
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SOC Home Page:
http://xmm.vilspa.esa.es/
Helpdesk web interface:
http://xmm.vilspa.esa.es/external/xmm_user_support/helpdesk.shtml
Helpdesk email address:
xmmhelp@xmm.vilspa.esa.es
News Mailing List:
http://xmm.vilspa.esa.es/external/xmm_user_support/xmm_news/
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Contents:
- New version of the XMM-Newton Science Archive is now available
- Status of the RGS/MOS cooling
New version of the XMM-Newton Science Archive is now available
==============================================================
Version 1.5 of the XMM-Newton Science Archive (XSA) is now available. To
start the Java-based user interface, please connect to the following URL:
http://xmm.vilspa.esa.es/xsa/
The user interface includes several new functionalities:
- The "Exposure" sub-panel of the "Query specification" panel allows
now full flexibility in the definition of queries on instrument modes.
Queries on "non science filters" (the EPIC "Calibration" suite: OM
"Blocked") are now possible
- The "Result Display Mode synchronization" button allows you to
automatically configure the exposure catalogue in accordance with the
instrument mode query. For example: if a query on MOS1 instrument modes
is done, the exposure catalogue may show only MOS1 records
- It is possible to expand individual records of an observation catalogue
into its constituent exposures
- Background light curve icons (extracted from the corresponding PPS
products FITS files) are available for display in the observation
catalogue
- A FITS viewer is available for quick interactive analysis of PPS images,
spectra and light curves
- A link is available besides each record of an observation catalogue to
a list of papers in refereed journals, which employed the corresponding
data. This link leads ultimately to the ADS entries. These links
are maintained in cooperation with the NASA HEASARC XMM-Newton Guest
Observer Facility
- The set of PPS products to be retrieved for each observation/exposure
in the shopping basket can be now defined according to a customized
menu. PPS products can be selected individually, by "categories" (event
lists, images, source lists, spectra, light curves, finding charts) or
by "groups" (EPIC products, RGS products, OM products, cross-correlation
products, pipeline products)
- PPS products can be downloaded as individual files (which can be
browsed in the ftp area before retrieval) or as a single tarfile
- Quota for retrieval via shopping basket is now on volume: 2 GBytes
for each XSA user, refreshed every 3 working days. In case you need
a temporary increase of this quota, do not hesitate to contact the
XMM-Newton HelpDesk (xmmhelp@xmm.vilspa.esa.es)
This version fixes also a few bugs:
- queries on revolution numbers larger than 426 are now possible
- whenever the proprietary rights expiry date is not available, the
string "Not available" is displayed in the corresponding field
of the observation catalogue record
A "Guided tour to the XSA" is available at the URL:
http://xmm.vilspa.esa.es/xsa/tour.html
together with a list of the known caveats for the current version:
http://xmm.vilspa.esa.es/xsa/xsa_caveats.html
Since an overwhelming majority of the XMM-Newton data users community
has been using the XSA as primary gateway to access their data,
XMM-Newton proprietary data will be distributed to their Principal
Investigators (PIs) through the science archive only, as of January 1,
2003. PIs interested to have their data on hard media as well can trigger
the generation of a CD-ROM through the XSA user interface.
The development of the XSA is an ongoing effort. The next public version
(2.0) is scheduled for spring-summer 2003. New functionalities expected
to be available in future near-term versions of the XSA include:
- queries on the average background rate during an observation
- visualization of EPIC source lists (as generated by the PPS pipeline
processing)
- "on-the-fly" filtering of event lists
- "on-the-fly" ODF reprocessing with the publicly available SAS
- interactive extraction of spectra (alongside the corresponding
response matrices) and light curves from a position defined via cursor
on an EPIC image
- access to the XMM-Newton catalogue
In the medium-term perspective, our main goal is to ensure a full
interoperability between the XSA and other archives and/or catalogue
facilities. This will imply the possibility of cross-queries between
different archives, and direct access to the XSA data content and/or
user interface from external facilities.
Do not hesitate to address any questions on the XSA content and
functionalities to the XMM-Newton HelpDesk (xmmhelp@xmm.vilspa.esa.es).
We wish you exciting science with the XMM-Newton data!
Status of the RGS/MOS cooling
=============================
In XMM-Newton News #25, dated 7-Nov-2002, plans to lower the operating
temperature of the RGS and MOS CCDs were described, the purpose of the
cooling being to move important detector characteristics back towards
the values which they had earlier in the mission.
Since then, excellent progress has been made in the cooling campaign,
with evidence of major improvements in detector performance. The RGS2
instrument was cooled on revolution 532, the MOS1 and MOS2 instruments
on revolution 533, and the RGS1 instrument on revolution 537. All
operations to change instrument operating temperatures are now
completed.
An initial appreciation of the results of the cooling can be had by
viewing the animated gif movies presented on the XMM-Newton web pages
at:
http://xmm.vilspa.esa.es/external/xmm_news/items/cooling02/index.shtml
These illustrate the evolution of a number of key parameters during
cooling.
RGS cooling
-----------
Through the night of Sunday to Monday, November 3 to 4, the RGS2 CCDs
were cooled towards a new operating temperature of -115 degrees C (RGS
Cool_A). The target Mkn 421 was observed through the night to track the
effects of the cooling. Towards the end of the night there were strong
indications that a slightly higher operating temperature might in fact
be needed in order to keep the detectors within the range of active
control by the heaters under the full range of possible thermal loading
on the instrument radiators. After careful subsequent assessment of the
data it was decided to establish the new RGS operating temperature
at -110 degrees C.
During perigee passage some excursion of the CCD temperature is now
seen to a few degrees above the set-point. But the nominal temperature
is re-established before resumption of science observations.
The main result of cooling for RGS2 is a huge reduction in the
incidence of flickering pixels. The CTI has been restored to close to
its pre-flight values. Previously poor CTI near the edges of the
detectors, where it had been x100 worse than for the inner regions, has
been almost eliminated. The CCD noise has been greatly lowered, and
the width of the noise distribution peak is now narrower than before
launch. There is now just one hot column and one hot pixel in RGS2.
During the night of Wednesday to Thursday, November 13 to 14, the RGS1
CCDs were also cooled to -110 degrees C (RGS Cool_B). After
preliminary analysis of the data, the improvements in RGS1 performance
are found to be entirely consistent with the RGS2 experience.
During Cool_B, re-tuning of the RGS CCD transfer clock voltages was also
concluded, completing the reconfiguration of the instrument. Where
necessary, small refinements of the calibration files needed to handle
data obtained in the period between Cool_A (rev.532) and Cool_B
(Rev.537) will be provided to users.
EPIC MOS cooling
----------------
Through the night of Wednesday to Thursday, November 6 to 7, the CCD
benches of both MOS instruments were cooled down to the new operating
temperature (-120 deg.C), reaching the new value within 2.75 hours.
The movies presented on the XMM-Newton web illustrate the reduction of
MOS line energy-width as a result of improved charge transfer
efficiency and show the decline of thermal defects during cooling.
The number of hot pixels has dropped by a factor of 7 (from 167 to 24)
for MOS2, and a factor of 2.6 (from 98 to 38) for MOS1. Now, on
average only 3 bad pixels are seen per CCD. The charge transfer
efficiency has improved by a factor of between 2 and 3, depending on
the CCD. The line-width and peak-height of spectral lines has improved
markedly. (Note: while the line widths are still being quantified for
the Rev.534 post-cooling measurements, the earlier trial cooling of
MOS2 in June of this year showed, for example, that the Mn K-alpha line
FWHM changed from 160eV to 140eV upon cooling).
Currently, the MOS CCDs undergo a temperature excursion during perigee
passage. They return to the new nominal operating temperature of -120
degrees C before the re-opening of the science window. There is a seasonal
variation in the thermal excursion and we are near, but not at, the
peak. This is unlikely to pose any problem for the instrument science
operations.
Redefinition of the calibration is proceeding on schedule.
Impacts of cooling on product distribution from SSC
---------------------------------------------------
In planning the cooling exercise, we have striven to keep any
consequent impacts on product distribution to a minimum. There is a
scheduled hold on product distribution from SSC in the period from
mid-November to mid-December to allow the derivation by the SOC and PI
teams of new, post-cooling, calibration files (CCFs) and consequent
revalidation of the processing chain. (The latest pre-cooling ODFs
(those from Rev.531) were exported from SOC to SSC on November 12, and
these will be the last ODFs processed with the pre-cooling calibration
files.)
The definitive re-calibration for the cooled RGSs will now come from
scheduled calibrations on Rev.546 (December 1 to 2). SSC product
distribution is expected to resume before Christmas, using preliminary
"cold" CCFs for RGS.
Monitoring for contamination
----------------------------
Specific contamination monitoring observations are underway to address
the remote possibility that, after cooling the detectors, any low level
ambient contaminants within the telescope/focal-plane subsystem might
start to freeze out onto the cold detector surfaces, although these are
still NOT the coldest points in the system by a significant margin. In
the event of any contamination appearing counter-measures will be taken
immediately.
Prospects for the end result
----------------------------
While intensive work is ongoing to fully evaluate changes in the
instrument performances following cooling, all indications are that the
exercise has been, as anticipated, extremely beneficial, with major
improvements in several key performance parameters.
The original hope that the RGS and EPIC MOS instruments would see key
performance characteristics restored to values which they had early, or
much earlier, in the mission, appears to be borne out.
Yours sincerely,
XMM-Newton SOC
***
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_/ XMM-NEWTON NEWS #25 --- 7-Nov-2002 _/
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ESA, XMM-Newton Science Operations Centre at
Villafranca del Castillo, Satellite Tracking Station
P.O. Box - Apdo. 50727, 28080 Madrid, Spain
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SOC Home Page:
http://xmm.vilspa.esa.es/
Helpdesk web interface:
http://xmm.vilspa.esa.es/external/xmm_user_support/helpdesk.shtml
Helpdesk email address:
xmmhelp@xmm.vilspa.esa.es
News Mailing List:
http://xmm.vilspa.esa.es/external/xmm_user_support/xmm_news/
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Contents:
- Users group meeting: minutes available online
- SAS web pages content reorganized
- New XMM-Newton Calibration Portal
- RGS/MOS cooling
- XMM-Newton Source Designations
- XMM-Newton On Board Time Wrap-Around Events
User group meeting: minutes available online
============================================
The XMM-Newton users' group met for the 2nd time on 16/17-Sep-2002 at VILSPA.
The users group made a number of recommendations which will impact future AO
review cycles; amongst which:
- Release date of AO-3
- Inclusion of large programs into the programme
- Revision of proposal review procedures
Please find the minutes of the meeting at :
http://xmm.vilspa.esa.es/external/xmm_user_support/usersgroup/index.shtml
SAS web pages content reorganized
=================================
Following a recommendation of the XMM-Newton User Group, the content of the SAS
web pages has been reorganized to provide the users with an easier access to
all the information necessary to reduce and analyze XMM-Newton data. The SAS
entry page is available at the following URL:
http://xmm.vilspa.esa.es/sas/
A top level, introductory, presentation of SAS and its capabilities is available
at the URL:
http://xmm.vilspa.esa.es/sas/documentation/
New XMM-Newton Calibration Portal
=================================
The new XMM-Newton Calibration Portal is online and available at the
following URL:
http://xmm.vilspa.esa.es/external/xmm_sw_cal/calib/
The new portal provides a clearer presentation of the XMM-Newton calibration
situation. The page gives all the necessary calibration information for all
XMM-Newton instruments (EPIC, RGS, OM) in order that a proper data
reduction may be undertaken.
The XMM-Newton calibration scientists and instrument teams have also prepared
documents describing the current status of the EPIC, RGS and OM calibration
as implemented in SAS 5.3.3. These are linked on the new XMM-Newton
Calibration Portal under the heading 'What is the current status of the
calibration?'.
RGS/MOS cooling
===============
Cooling of the RGS and EPIC MOS instruments
-------------------------------------------
During November and December 2002 a series of operations will be
performed on the RGS and EPIC MOS instruments in order to lower the
nominal operating temperatures of their detectors, and subsequently
re-establish the calibration of the instruments. The purpose of the
cooling is to move important detector characteristics back towards
the values which they had earlier in the mission.
Radiation effects on detector performance
-----------------------------------------
Since the start of the XMM-Newton mission the RGS CCDs have been
operated at a temperature of -80 degrees C, and the MOS detectors at a
temperature of -100 degrees C. Over these first three years of the
orbital mission the daily passage of the spacecraft through the Earth's
radiation belts, combined with irregularly occurring Solar Flares, have
subjected the CCDs to high (but predicted and expected) levels of
ionizing radiation.
Resulting changes in the operating characteristics of the detectors were
anticipated before launch, and instrument design and ground testing
provided for the eventual implementation of corrective measures
in-flight.
At this point in the mission, ongoing calibration monitoring has
demonstrated that the Charge Transfer Efficiency (CTE) of the EPIC MOS
CCDs has degraded somewhat relative to its value immediately after
launch. As a result the energy resolution achievable has fallen and,
for example, the measured energy width of the Mn and Al lines has
increased 15 to 20% above its original value. For RGS, the main effect
of the ionizing radiation dose has been a significant increase in the
number of "hot pixels" and of resulting bad columns affecting RGS
spectra.
Restoration of performance
--------------------------
At the second XMM-Newton Users Group meeting, held in September of this
year, it was agreed that the time had come to implement the
long-envisaged mitigating strategy. That is to reduce the operating
temperature of the detectors. Such a reduction in operating temperature
is expected to lead to the recovery of most of the original performance
levels of the RGS and MOS detectors. (A test, made in June of this year
demonstrated that cooling the MOS2 instrument to an operating
temperature of -120 degrees C led to recovery of most of its original
CTE.)
The Users Group therefore urged the XMM-Newton SOC team to explore
approaches to cooling the RGS and EPIC MOS instruments and
re-establishing their calibration while causing minimum delays in
distribution of reduced data products to observers.
Instrument cooling and re-calibration
-------------------------------------
As a result, in a campaign starting on November 4 just after midnight
at Villafranca, and extending through November and into early December,
the instruments will be cooled and recalibrated according to the
schedule below :
Nov. 4 to 5, Rev.532 Cool RGS2 from -80 to -115 degrees and
recalibrate
Nov. 6 to 9, Rev.533/534 Cool MOS1 and 2 from -100 to -120 degrees
and recalibrate
Nov.14 to 15, Rev.537 Cool RGS1 from -80 to -115 degrees and
recalibrate
Dec. 2 to 3, Rev.546 Check RGS 1&2 calibration after some weeks
cold.
For most of the intervening revolutions normal scientific observations
will continue, although as time progresses these will increasingly
relate to the new, reduced, operating temperatures and new values of
certain calibration parameters.
Throughout the above period, interleaved (re-)calibration and
contamination monitoring observations will be fed to immediate
interactive data analysis, and updated calibration files (CCFs) will be
derived for the Science Analysis System (SAS). In this way the overall
interruption in pipeline data product distribution is expected to be
confined to a very limited period from mid-November to mid-December, 2002.
Updated CCFs will be made available to SAS users in the December/January
time frame.
Monitoring for contamination
----------------------------
Specific contamination monitoring observations will address the remote
possibility that, upon cooling the detectors, any low level ambient
contaminants within the telescope/focal-plane subsystem might start to
freeze out onto the cold detector surfaces, although these will still
NOT be the coldest points in the system by a significant margin. In
the event of any contamination appearing counter-measures will be
taken immediately.
The end result
--------------
The full series of operations, calibrations and calibration file
derivations, along with a comprehensive schedule of tracking meetings,
will give the months of November and December at VilSpa something with
the complex character of operations like an early orbit phase. At the
end of these activities it is hoped that the RGS and EPIC MOS
instruments will see key performance characteristics restored to values
which they had early in the mission, with immediate benefit for science
data quality and minimal ongoing impact on the service provided to the
observer community.
XMM-Newton Source Designations
==============================
As reported in XMM-Newton News #6, a naming convention for the XMM-Newton
sources detected by individual researchers was approved by the IAU "Clearing
House" of Commission 5 Working Group on Designations. Details on this
naming convention have been summarized now at :
http://xmm.vilspa.esa.es/external/xmm_science/src_naming.shtml
XMM-Newton On Board Time Wrap-Around Events
===========================================
Maintaining accurate time stamps for all events on-board XMM-Newton is a
very complex procedure. The XMM-Newton SOC is in the process of generating
an accurate, full, end-to-end description of all elements relevant to
deriving accurate timing. One of the elements crucial in the entire chain
is the so-called "Central Data Management Unit" (CDMU) which distributes
and generates the on-board master clock. The CDMU master clock has a finite
number of bits to represent time, and as such every so often this clock
wraps around. Although these wrap-around (and other) events should be
transparent to the end-user when using the SAS or the PPS products to
look at your data, we will make all information available on the WWW, if
only as a reference. The first in this series is the CDMU.
After a CDMU reset or a wrap-around, the XMM-Newton instruments' clocks and
the CDMU have to re-synchronized. This is either a manual procedure or it
automatically occurs at instrument switch-on.
SOC has published now a table indicating when the clocks re-synchronization
took place for each event (and the potential impact associated with the delay
between on-board clock re-start and instruments' clocks re-synchronization).
Information on all past CDMU Clock Events as well as the next predicted
wrap-around have been made available at the following URL:
http://xmm.vilspa.esa.es/external/xmm_user_support/documentation/clock_events.shtml
Yours sincerely,
XMM-Newton SOC
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