B/chandra The Chandra Archive Log (CXC, 1999-2014)
Exposure Catalog from Chandra X-Ray Observatory (CXC Team)
<Chandra X-Ray Observatory Science Center (USA)>
=2002yCat....102007C 2002yCat....102007C
ADC_Keywords: Observatory log ; X-ray sources
Mission_Name: Chandra
Description:
The Chandra X-Ray Observatory (CXO) is a high-resolution (< 0.5
arcsecond) X-ray telescope with a suite of advanced imaging and
spectroscopic instruments. The Observatory was successfully launched
by NASA's Space Shuttle Columbia on July 23, 1999.
Chandra was designed to provide order-of-magnitude advances over
previous X-ray astronomy missions with regards to spatial and spectral
resolution. The High Resolution Mirror Assembly (HRMA) produces images
with a half-power diameter (HPD) of the point spread function (PSF) of
< 0.5 arcsec.
Chandra has two focal plane science instruments, i) The Advanced CCD
Imaging Spectrometer (ACIS), and ii) The High Resolution Camera (HRC).
ACIS is comprised of two CCD arrays, a 4-chip array, ACIS-I ; and a
6-chip array, ACIS-S . ACIS-I was designed for CCD imaging and
spectrometry; ACIS-S can be used both for CCD imaging spectrometry and
also for high-resolution spectroscopy in conjunction with the HETG
grating. A mix of ACIS-S and ACIS-I chips (up to six) may be used
for imaging observations. The HRC is comprised of two microchannel
plate (MCP ) imaging detectors: the HRC-I designed for wide-field
imaging; and, HRC-S designed to serve as a readout for the LETG .
The grating systems consist of the Low Energy Transmission
Grating (LETG) and the High Energy Transmission Grating (HETG).
The HETG , when operated with the HRMA and the ACIS-S , forms the
High-Energy Transmission Grating Spectrometer (HETGS ) for high
resolution spectroscopy . The HETGS achieves resolving power up to
1000 in the band between 0.4 keV and 10.0 keV.
The LETG when operated with the HRC-S , forms the Low Energy
Transmission Grating Spectrometer (LETGS ). The LETGS provides the
highest spectral resolution on Chandra at low (0.08 - 0.2 keV)
energies.
This catalogue is a copy of the Chandra Observation Catalog from the
Chandra Data Archive (CDA) which is part of the Chandra X-Ray
Observatory Science Center (CXC) which is operated for NASA by the
Smithsonian Astrophysical Observatory.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
chandra.dat 240 27319 The Chandra Log (2025-08-10)
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See also:
http://cxc.harvard.edu/ : the CXC Home page
http://cxc.harvard.edu/cda : the Chandra Data archive home page
Byte-by-byte Description of file: chandra.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- SeqNum Sequence Number (1)
8- 12 I5 --- ObsID Observation ID (2)
14- 19 A6 --- Instr Instrument (3)
21- 28 A8 --- Mode Observing mode for ACIS instrument (4)
30- 33 A4 --- Grat Grating (5)
35- 41 F7.3 ks AppExp Approved exposure time (ks)
43- 51 F9.3 ks ExpTime ? Exposure time (ks)
53- 92 A40 --- Target Target Name as specified in proposal
94-112 A19 --- PIname Name of Principal Investigator
114-122 F9.5 deg RAdeg ? RA in J2000 decimal degrees
124-132 F9.5 deg DEdeg ? Dec in J2000 decimal degrees
134-151 A18 --- Status Status of the observation (6)
153-156 I4 yr ObsDate.Y ? Start Observation date (year)
157 A1 --- --- [.]
158-159 I2 "month" ObsDate.M ? Start Observation date (month)
160 A1 --- --- [.]
161-162 I2 d ObsDate.D ? Start Observation date (day)
164-165 I2 h ObsDate.h ? Start Observation date (hour)
166 A1 --- --- [:]
167-168 I2 min ObsDate.m ? Start Observation date (minute)
169 A1 --- --- [:]
170-171 I2 s ObsDate.s ? Start Observation date (second)
173-176 I4 yr PubDate.Y ? Public release date "YYYY.MM.DD"
177 A1 --- --- [.]
178-179 I2 "month" PubDate.M ? Public release date "YYYY.MM.DD"
180 A1 --- --- [.]
181-182 I2 d PubDate.D ? Public release date "YYYY.MM.DD"
184-186 A3 --- Type Type of observation (7)
188-195 I08 --- PrNum ? Proposal Number
197-238 A42 --- Category Category of the observed target (8)
240-241 I02 --- AO Announcement of opportunity (proposal round)
Note (1): Sequence Number.
The Sequence Number is the largest unit, defined by the proposal
approval process. It is conceptually a single observation with a
certain amount of approved time. At this level we do the bookkeeping
on the amount of observing time used and the date when the data go
public. The data distribution uses the SeqNum as the name of the
top-level directory for the data. The actual observation may be done
under one or more ObsIds.
Note (2): Observation ID.
The Observation Id indicates an observation of a specified target, for
a specific proposal, with a specific observational configuration
(i.e., when different parts of a SeqNum are observed with different
configurations - e.g., different ACIS chips - they will receive
separate ObsIds). All data for a given ObsId are always combined in a
single set of Level 2 products.
Note (3): Instruments
The two Chandra instruments are ACIS (Advanced CCD Imaging
Spectrometer) and HRC (High Resolution Camera); each has a spectral
and an imaging component.
Note (4): Observing mode
For the ACIS instrument, it is of the form
Ty_xxxxx = Timed Exposure,
CC_xxxxx = Continuous Clocking
where y is an upper case letter and x is a hexadecimal digit.
For HRC it is DEFAULT for most observations.
Note (5): Transmission gratings:
LETG (commonly used with HRC) and
HETG/METG (commonly used with ACIS).
Note (6): Status of the observation. Possible entries are:
archived, observed, partially observed, scheduled,
unobserved, canceled, discarded
Note (7): Type of observation:
GO Guest Observer
GTO Guaranteed Time Observation
CAL Calibration
TOO Target Of Opportunity
DDT Director's Discretionary Time
Note (8): Categories are:
Solar System and Misc.
Normal Stars and WD
WD Binaries and CV
BH and NS Binaries
SN, SNR and Isolated NS
Normal Galaxies
Active Galaxies and Quasars
Clusters of Galaxies
Extragalactic Diffuse Emission and Surveys
Galactic Diffuse Emission and Surveys
Acknowledgements:
It is a pleasure to thank Arnold Rots for his help in the preparation
of this document.
* 19-Jun-2005: Change in the format
(Target column increased from 33 to 41 bytes)
(End) Mark Allen [CDS] 15-Feb-2002