XMMNewton RGS detector performance tools

1
XMM-Newton RGS detector performance tools Carlos
GABRIEL - RSSD ESA - XMM Newton SOC, Madrid,
Spain Jan-Willem den HERDER, Cor de VRIES -
SRON, National Institute for Space Research,
Utrecht, the Netherlands

• XMM-Newton Telescope characteristics
• 3 x 58 concentric mirror shells
• Au-coated electroformed nickel shells
• Held by spider with 16 arms
• Triangular PSF (dependent on XRT) with FWHM
  5 (little variation over wide energy range)
• Large effective area ( 4650 cm2 at 1.5 keV)
• High straylight rejection through X-ray baffles

XMM-Newton The most sensitive X-ray satellite
ever built, has been operating successfully
since begin of 2000. It is providing the
scientific community with the deepest X-ray
spectral images ever along more than two
decades in energy (0.1 - 15. keV) through its
three EPIC cameras (pn, MOS1, MOS2), as well as
with high resolution spectra (resolving
power of 200-800 ) in the soft X-rays
(0.5-2.2 keV) through the two grating
spectrometers RGS1 and RGS2. Simultaneous
optical and UV coverage is ensured by the
Optical Monitor (OM) on board. XMM-Newton can
observe simultaneously with all 6 instruments
through its 4 telescopes three barrel-shaped
Mirror Modules, each containing 58 wafer-thin
concentric mirrors for focusing X-ray radiation
and a 30 cm optical telescope for visible
and UV imaging, including grism spectral
capability.
XMM-Newton was launched with an Ariane 5
rocket from Kourou Guyana on December 10, 1999
Example of data corresponding to the observation
of the star Capella. The color scale represents a
logarithmic intensity scale. The top panel shows
the image of dispersed light on CCDs
horizontally. The bottom panel shows the order
selection plane, with the energy on the ordinate.
This is used for separating 1 and 2 grating
orders onto the RGS focal plane.
Reflection Grating Spectrometers (RGS) Behind
two of its three nested sets of Wolter I
type mirrors, XMM-Newton carries two
identical spectrometers, designed to perform
high resolution X-ray spectroscopy
(E/DE100-500) in the range 0.3-2.1 keV.
Optimized for observing the K-shell
transitions of carbon, nitrogen, oxygen, neon,
magnesium and sillicon, as well as the L-shell
transitions of iron, the RGS have together a
maximum effective area of about 140 cm2 at 0.9
keV. Each RGS is built of an array of 182
precisely aligned reflection gratings (RGA),
intercepting about half of the light
passing through the telescope, and a
focal plane camera (RFC), composed of nine
large format back illuminated CCDs for
detection of the dispersed spectra in single
photon counting mode.
Dispersion equation cos b cos a ml / d
Audard et al. 2001, AA 365
Detailed analysis of the spectral features (as
done with the Capella data here) permits
determination of abundance, density,
temperature, ionisation state, mass motion and
velocity shift of emitting region and surrounding
environment. Detailed modeling can be applied
thanks to the extraordinary resolution and high
throughput.
The RGS Diagnostic Tools
Diagnostic Analysis Tools I Data reduction and
DB population
The RGS performance tools Continuous monitoring
of instrument health and performance is done
using the different data types. In addition
to on-line monitoring of continuous HK data
telemetry, dedicated tools dealing with
Diagnostic and Science Data derive eg. dark
currents, charge transfer efficiencies, system
noise level, establish hot pixels and columns,
create databases used for monitoring and trend
analysis purposes.
Digestion of Diagnostic Data into variables
showing instrument performance
RGS position and width of system peak (
offset distribution) per CCD pixels with
rates above detection threshold (non X-ray
events, hot pixels) rejected events,
expected rates, ... composite image of
diagnostic frames
Output postscript file (per revolution)
with numerical and graphical output IDL
structure with all the variables per exposure
used for postscript file IDL structure
containing averaged results of system peak per
CCD and node Diagnostic Image per exposure for
easy retrieval and analysis

• RGS Operating Modes
• Actually in use spectroscopy diagnostic
• Spectroscopy
• 9 CCDs read out sequentially within 5.7 seconds
  (3x3 On-Chip-Binning) with
• low signal threshold applied, hot columns and
  hot pixels rejection (look-up table)
• programmable on-board processor selection of
  X-ray like events by event pattern
• Main products event list containing
  4-dimensional X-ray events (X,Y,E,t)
• gt projections X-ray images (Xb,Y), spectra
  (E, X,Y), light curves (t, X,Y)
• through dispersion and selection maximum
  resolution in b gtgt high resolution spectroscopy
• Diagnostic
• full images stored on board and transferred to
  ground
• Normal operating mode Spectroscopy interleaved
  Diagnostic (every 20 minutes 1 CCD full image)

gtgtgt Database containing all the described
output on line
Diagnostic Analysis Tools II Trend
Analysis and calibration derivation Package for
analysis of instrument evolution / degradation /
malfunctioning with time
Four different areas System peak analysis
General Diagnostic Hot pixels / columns
General Image viewer
Input General Diagnostic DB System Peak
DB Diagnostic images DB Bad pixels images
(also output)

• Output
• System peak
• plots of main values and amplitude vs time per
  CCD and node
• system peak evolution fits
• General diagnostic data same as by Diagnostic
  Tools (covering longer periods)
• Hot pixels frequency images, bad pixel
  tables, temporal evolution of BP flag
• Diagnostic Images
• individual and movie access for eg. detection
  of anomalies
• used for derivation of RGS offset files

The RGS Science Tools
Package for analysis of instrument evolution /
degradation / calibration using Science Data

• Producing e.g.
• Basic event reconstruction and signal offset
  subtraction
• Hot / warm pixels detection measure of soft
  proton background
• Display of CCD spatial and energy images,
  including events selection regions
• Extraction of background subtracted 1st order
  spectrum
• Estimation of source and background counts in
  1st and 2nd order
• Fits of calibration source spectra to get
  pulse-height positions and count rates.

Trend analysis bad pixel percentage evolution
continuous increase due to radiation damages,
jumps caused by solar flares, sudden decrease
by change of working CCD temperature
Summary file and calibration source analysis file
corresponding to the analysis of a single RGS
science exposure
The RGS Monitoring Pages Optimal use of
monitoring results through publication on web
pages, containing tables, plots, images. Produced
automatically every night through batch mode runs
of RGS Diagnostic and Science Tools, they contain
the most relevant data for a regular checking of
the instrument functioning.