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Chandra Electronic Bulletin No. 41
             |                                            |
             |              CCC  XX   XX    OOO           |
Chandra      |             CC     XX XX    OO OO          | CXC
Electronic   |            CC       XXX    OO   OO         | Number 41
Bulletin     |             CC     XX XX    OO OO          | August
             |              CCC  XX   XX    OOO           | 2005
             |                                            |

Welcome to the Chandra X-ray Center's Electronic News Bulletin Number 41.

CXC Web site: cxc.harvard.edu

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1.  Revised Policy regarding Completion of Chandra Observations

2.  Six Years of Science with Chandra Symposium: 
            Abstract Deadline is Fast Approaching! 

3.  Chandra Calibration Workshop  


Item 1.  Revised Policy regarding Completion of Chandra Observations

 In general, an observation, defined as corresponding to a unique sequence 
number, will be considered complete when 90% or more of the requested time has 
been observed, as determined by the Good Time Interval (GTI) in the processed 
data relative to the approved time. (Previous policy set this threshold at 

 The following 4 exceptions are identified:

1. TOO and DDT observations with GTI less than 90% of the requested time may 
be declared complete by the CXC Director or his representative when 
constraints due to competing targets and/or observatory restrictions do not 
allow the full time (or 90% of it) to be achieved and when a subsequent 
observation would no longer meet the objectives. Such cases will be tracked 
and closed by adjusting the approved observing time in OBSCAT after final 
scheduling is completed.
2. For observations (unique sequence number) greater than 200 ksec, any 
remaining time exceeding 20 ksec will be scheduled even if the GTI to approved 
time ratio exceeds 90%, provided constraints allow.

3. For observations less than 5 ksec, targets will be observed only once and 
will be considered complete regardless of the GTI achieved unless a spacecraft 
anomaly causes the entire observation to be missed.
4. For observations with less than 2 ks remaining, no additional time will be 
scheduled even if the 90% GTI to requested time has not been achieved.

Items 1 and 2 are implemented as of July 8, 2005. This new policy will not be 
applied to observations completed prior to July 8 and there will be no impact 
on their previously assigned public release dates. Release dates established 
after July 8, 2005 may be incorrect for a few observations affected by the new 
policy, until updated software is available to fully implement the changes. 
For such cases the release dates will be corrected manually at least 6 months 
prior to the public release.

Items 3 and 4 are intended to avoid additional short exposures with their 
relatively high fractional overhead (inefficient use of Chandra). Item 4 
assures that observations between 5 and 20 ks get at least 60% of their 
approved time (for 5 ks approved) with a sliding scale assuring that at least 
90% is achieved when we reach 20 ks approved time. These two modifications 
will be discussed with the Chandra Users Committee at the October 2005 
meeting, and if supported by the CUC they will be implemented around Dec 1, 
2005 at the transition from Chandra Cycle 6 to Cycle 7. Current rules covering 
these observation ranges would remain in effect until December 1, 2005 and for 
all Cycle 6 targets until completed.

 Note: The proprietary time begins when the observation is "complete"
according to the above rules.


Item 2. Six Years of Science with Chandra Symposium: 
               Abstract Deadline is Fast Approaching!

The abstract and registration deadlines for the symposium are
SEPTEMBER 1, 2005.

The astronomical community is strongly encouraged to propose oral and/or
poster contributions for the symposium.  Abstracts should be submitted 
on-line at


Full information on the symposium can be found on the web site at:


Antonella Fruscione
and the SOC and LOC committees


Item 3.   Chandra Calibration Workshop

The 2005 Chandra Calibration Workshop will be held on
October 31 and November 1 at the Royal Sonesta Hotel
in Cambridge, immediately preceding the Chandra 6 Years

The CCW is intended to share the Chandra teams' knowledge
of the detectors and mirrors with the community while
encouraging participation and feedback in the process of
calibrating the satellite.  Presentations are solicited
on aspects of Chandra calibration and its effects on data
analysis and interpretation.

To register, and to submit abstracts, go to


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Last modified: 12/03/10

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