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Dear CHANDRA Observer,
I will be the Uplink Support Interface (USINT) contact for your
LETGS/ACIS-I observation of [target] throughout the
"uplink cycle", i.e., until your photons are collected by Chandra. I
am contacting you now to request that you confirm your observation
set-up by day-month-year.
The above date is determined by the deadline for building the
appropriate satellite command loads. It is important to note that
after that time it will not be possible to change any of the
observation parameters (unless your observation is a TOO and future
contact will be necessary). If you are in any doubt as to the
instrument set-up you require, or if you have any questions concerning
your observation, please do not hesitate to contact me. Correspondence
via email is preferred (cc to "cus@head-cfa.harvard.edu"), but you
may also contact me by phone or FAX (see below). If the set-up is
correct as it is, I still require your confirmation.
Your observation is currently scheduled for the week of day-month-year
as seen in the Long Term Schedule at
http://cxc.harvard.edu/target_lists/longsched.html.
You can check your observation parameters in the on-line OBSCAT by going to
http://cxc.harvard.edu, clicking on "Target Search Page," and then using
the search facility to find your "Summary of Sequence Number" page.
Please check that page for accuracy of the following in particular:
* the target name,
* the target coordinates (in decimal degrees),
* the exposure time (in kilo-seconds),
* the target offset (in arcminutes),
* the defocus (in mm),
* the SIM-Z (detector translation, in mm),
* the roll constraint (in degrees),
* the time constraint.
* the HRC configuration or ACIS mode
You can view the orientation of the detector on the sky in the optical
and X-ray bands by clicking on the "DSS" (Digital Sky Survey),
"ROSAT" (pointed observation, if any), and "RASS" (ROSAT All-Sky
Survey) buttons at the bottom of the page. Please note that if your
observation is a TOO, the roll angle will of course be unknown; the
DSS, ROSAT, and RASS images are shown assuming a roll angle of 0
degrees. The range of permitted roll angles vs date is illustrated
via the "Roll/Visibility" button.
Please be advised that the following changes in your observing program are
not generally permitted:
* adding any constraints,
* changing exposure time or target,
* adding or removing a grating, or
* switching between ACIS and HRC or LETG and HETG so that
the target and instrument configuration end up being the same
as in someone else's observing proposal.
If you request changes, I will confirm these with you by e-mail (or
telephone), and after about two days you should see these updated
parameters in the on-line OBSCAT database.
In considering your observation set-up, I draw your attention to
aspects of the current in-flight performance of the LETG/ACIS-S
combination that you might need to consider when deciding your final
set-up. These issues are discussed in detail in the Chandra Proposer's
Observatory Guide, but as a reminder I list the main ones:
1) To ameliorate the effects of Charge Transfer Inefficiency on the
front-side illuminated chips for spectral order sorting, the
default LETG observation set-up for a point source uses a SIM-Z
offset of -8mm, which places the source nearer to the CCD
framestore region. If your source is extended please contact me
so that we can determine an optimum source placement on the ACIS
detector.
2) If your source is particularly bright, pile-up could be an issue
for the dispersed spectrum as well as for 0th order.
A summary of these and other issues (including offsets and subarrays)
can be found via http://cxc.harvard.edu/ by clicking on the
"Instruments and Calibration" button and then "LETG". The direct
URL is http://cxc.harvard.edu/cal/Links/Letg/User/.
Again, if you have any questions at all about the set-up and execution
of your LETGS observation please do not hesitate to contact me.
Last modified: 05/02/03
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The Chandra X-Ray
Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA. Email: cxcweb@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2004. All rights reserved. |