| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This dataset contains calibrated images of comet 9P/Tempel 1
acquired by the Medium Resolution Instrument Visible CCD (MRI) from
01 May through 05 July 2005 during the encounter phase of the Deep
Impact mission.
Version 3.0 was calibrated by the EPOXI mission pipeline and includes
corrected observation times and a revision to how the camera's
compressed zero-DN lookup table entry is decoded. The EPOXI pipeline
corrected the interpretation of microsecond counter of the spacecraft
clocks which introduced maximum errors of about 40 milliseconds in the
earlier Versions 2.0 and 1.0 of this dataset that were produced by the
Deep Impact pipeline. The EPOXI pipeline was also changed to decompress
the visual CCD camera's zero-DN lookup table entry to the top of its
range, which is 350 DN, and flag the affected pixels as saturated.
For Version 3.0, the I-over-F data products archived in Version
2.0 were replaced by multiplicative constants supplied in the headers
for converting radiance products to I-over-F, and the EPOXI convention
for constructing PRODUCT_IDs and data file names was used. Finally
for this version, a horizontal stripes removal process and improved
absolute radiometric calibration constants were applied by the
calibration pipeline. For more information see the EPOXI Calibration
Pipeline Summary document in this dataset and Klaasen, et al. (2013)
[KLAASENETAL2011].
A summary of the comet observations in this data set is provided here:
Mid-Obs Exposure IDs
Date DOY Minimum Maximum Mission Activity
---------- --- ------- ------- --------------------------
2005-05-01 121 5000104 5000111 Daily Comet Imaging
2005-05-07 127 5000704 5000723 Daily Comet Imaging
2005-05-08 128 5000804 5000847 Daily Comet Imaging
2005-05-15 135 5001504 5001599 Daily Comet Imaging
2005-05-16 136 5001604 5001671 Daily Comet Imaging
2005-05-17 137 5001704 5001771 Daily Comet Imaging
2005-05-18 138 5001804 5001871 Daily Comet Imaging
2005-05-19 139 5001904 5001971 Daily Comet Imaging
2005-05-25 145 5002504 5002571 Daily Comet Imaging
2005-05-26 146 5002604 5002659 Daily Comet Imaging
2005-05-27 147 5002700 5002759 Daily Comet Imaging
2005-05-28 148 5002800 5002835 Daily Comet Imaging
2005-05-29 149 5002900 5002971 Daily Comet Imaging
2005-05-30 150 5003000 5003071 Daily Comet Imaging
2005-05-31 151 5003100 5003123 Daily Comet Imaging
2005-06-03 154 6000300 6000371 Daily Comet Imaging
2005-06-04 155 6000400 6000471 Daily Comet Imaging
2005-06-05 156 6000500 6000523 Daily Comet Imaging
2005-06-10 161 6001012 6001035 Daily Comet Imaging
2005-06-11 162 6001100 6001147 Daily Comet Imaging
2005-06-12 163 6001200 6001223 Daily Comet Imaging
2005-06-13 164 6001300 6001359 Daily Comet Imaging
2005-06-14 165 6001400 6001447 Daily Comet Imaging
2005-06-15 166 6001500 6001571 Daily Comet Imaging
2005-06-16 167 6001600 6001635 Daily Comet Imaging
2005-06-17 168 6001700 6001759 Daily Comet Imaging
2005-06-18 169 6001800 6001847 Daily Comet Imaging
2005-06-19 170 6001900 6001971 Daily Comet Imaging
2005-06-20 171 6002000 6002071 Daily Comet Imaging
2005-06-21 172 6002100 6002171 Daily Comet Imaging
2005-06-22 173 6002200 6002271 Daily Comet Imaging
2005-06-23 174 6002300 6002371 Daily Comet Imaging
2005-06-24 175 6002400 6002471 Daily Comet Imaging
2005-06-25 176 6002500 6002559 Daily Comet Imaging
2005-06-26 177 6002600 6002647 Daily Comet Imaging
2005-06-27 178 8000003 8000143 Daily Comet Imaging
2005-06-28 179 8000168 8000176 Daily Comet Imaging
8100000 8100140 Daily Comet Imaging
2005-06-29 180 8100165 8100173 Daily Comet Imaging
8200000 8200107 Daily Comet Imaging
8300003 8300011 Daily Comet Imaging
2005-06-30 181 8400042 8400050 Daily Comet Imaging
8400129 8400482 Daily Comet Imaging
2005-07-01 182 8400561 8400569 Daily Comet Imaging
8500000 8500437 Daily Comet Imaging
2005-07-02 183 8500477 8500533 Daily Comet Imaging
8600000 8600167 Daily Comet Imaging
8800015 8800179 Radiometry and Imaging
2005-07-03 184 9000003 9000340 Continuous Comet Imaging
2005-07-04 185 9000341 9001067 Impact Imaging
9010000 9080000 Lookback Imaging
2005-07-05 186 9080000 9120000 Lookback Imaging
2005-07-06 187 9120000 9150017 Lookback Imaging
The 9P/Tempel 1 data are described in 'Deep Impact: The Anticipated
Flight Data' by Klaasen, et al. (2005) [KLAASENETAL2005]. Initial
results from the encounter and impact were presented in 'Deep Impact:
Excavating Comet Tempel 1' by by A'Hearn, et al. (2005)
[AHEARNETAL2005A].
Required Reading
---------------
The documents listed below are essential for the understanding and
interpretation of this dataset. Although a copy of each document is
provided in the DOCUMENT directory of this dataset, the most recent
version is archived in the Deep Impact and EPOXI documentation set,
DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V4.0, available online at
http://pds.nasa.gov.
EPOXI_SIS.PDF
- The Archive Volume and Data Product Software Interface
Specifications document (SIS) describes the EPOXI datasets
including this Deep Impact dataset recalibrated by the EPOXI
pipeline, the science data products, and defines keywords in
the PDS labels.
EPOXI_CAL_PIPELINE_SUMM.PDF
- The EPOXI Calibration Pipeline Summary provides an overview
of the final version of the calibration pipeline that generated
the data products in this dataset. For a thorough discussion
of the pipeline, see 'EPOXI Instrument Calibration' by Klaasen,
et al. (2013) [KLAASENETAL2011].
CALIBRATION_PAPER_DRAFT.PDF
- This incomplete draft of 'Deep Impact Instrument Calibration'
by Klaasen, et al. (2008) [KLAASENETAL2006] explains how the
instruments were calibrated for the Deep Impact mission. It
also describes the Deep Impact calibration pipeline, which was
the basis for the EPOXI calibration pipeline.
INSTRUMENTS_HAMPTON.PDF
- The Deep Impact instruments paper by Hampton, et al. (2005)
[HAMPTONETAL2005] provides very detailed descriptions of the
instruments.
MRI_ENCOUNTER_DATA_SUMMARY.PDF
- This log provides notes and data quality recorded by the science
team for each MRI image, beginning 28 hours before impact and
continuing through the lookback period.
MRI_3_4_DI_TEMPEL1.TAB
- This ASCII table provides image parameters such as the mid-obs
Julian date, exposure time, image mode, filter, mission activity
type, and description or purpose for each observation (i.e., data
product) in this dataset. This file is very useful for
determining which data files to work with.
Related Data Sets
-----------------
The following PDS datasets are related to this one and may be useful
for research:
DIF-CAL-HRII/HRIV/MRI-2-GROUND-TV4-V1.0
- Raw MRI pre-flight calibration images from the fourth thermal
vacuum test in 2003
DIF-CAL-MRI-2-9P-CRUISE-V1.0
- Raw MRI cruise calibration images
DIF-C-MRI-3/4-9P-ENCOUNTER-V2.0
- Raw MRI images of comet Tempel 1
DIF-C-HRII/HRIV/MRI-6-TEMPS-V1.0
- HRII, HRIV, and MRI instrument thermal telemetry data from the
Deep Impact mission which may be useful for determining how
temperature fluctuations affect the science instruments, in
particular the HRII spectrometer
DI-C-SPICE-6-V1.0
- Deep Impact SPICE kernels
DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V4.0
- Deep Impact and EPOXI documentation set
Processing
==========
The calibrated two-dimensional FITS CCD images and PDS labels in this
dataset were generated in late 2013 by the EPOXI data pipeline,
maintained by the project's Science Data Center (SDC) at Cornell
University. Known limitations and deficiencies of the pipeline and
the resulting data are discussed in the EPOXI Calibration Pipeline
Summary document in this dataset and by Klaasen, et al. (2013)
[KLAASENETAL2011] and in 'Deep Impact Instrument Calibration' by
Klaasen, et al. (2008) [KLAASENETAL2006].
For each CCD image, the pipeline generates two types of calibrated
products:
- Uncleaned radiance data provided in units of
Watts/(meter**2 steradian micron) and identified by the
mnemonic 'RADREV'. The RADREV data are considered to be
reversible because the calibration steps can be backed out to
return to the original, raw data numbers. A RADREV image can
be converted to unitless I-over-F by multiplying by the value
assigned to the DATA_TO_IOVERF_MULTIPLIER keyword in the PDS
label. Alternatively, a RADREV image can be converted from
radiance units to calibrated data numbers by multiplying by the
value assigned to the DATA_TO_DN_MULTIPLIER in the PDS label.
- Irreversibly cleaned radiance data provided in units of
Watts/(meter**2 steradian micron) and identified by the
mnemonic 'RAD'. The RAD data are considered to be
irreversible because the calibration steps, such as smoothing
over bad pixels, cannot easily be backed out to return to the
original, raw data numbers. A RAD image can be converted
to unitless I-over-F by multiplying by the value assigned to
the DATA_TO_IOVERF_MULTIPLIER keyword in the PDS label.
Alternatively, a RAD image can be converted from radiance units to
calibrated data numbers by multiplying by the value assigned to
the DATA_TO_DN_MULTIPLIER in the PDS label (though interpolated
pixels will not be real data). Please note that values in the
overclock rows and columns bordering the active CCD area are
set to 0 in the RAD product.
The calibration pipeline performed the following processes, in the
order listed, on the raw FITS data to produce the RADREV and
RAD products found in this dataset (the process uses the image
mode and filter to select the appropriate set of calibration files):
- Decompression of compressed raw images (compression was performed
on board the spacecraft and the resulting data were downlinked)
- Correction for bias
- Subtraction of a dark frame
- Removal of horizontal, instrumental striping
- Removal of electronic cross-talk
- Application of a normalized flat field
- Removal of CCD transfer smear
- Conversion of data numbers to units of radiance for an absolute,
radiometric calibration that is reversible (RADREV)
- Interpolation over bad and missing pixels identified in the
RADREV data to make a partially cleaned, irreversible, radiometric
calibration with units of radiance (RAD); Steps for despiking
(i.e., cosmic ray removal) and denoising the data which are part
of the RAD stream were not performed because the existing routines
are not robust
- Calculation of multiplicative factors to convert a RADREV or RAD
image to I-over-F
As part of the calibration process, the pipeline updated the
pixel-by-pixel image quality map, the first FITS extension, to identify:
- Pixels where the raw value was saturated,
- Pixels where the analog-to-digital converter was saturated,
- Pixels that were ultra-compressed and thus contain very little
information, and
- Pixels considered to be anomalous as indicated by bad pixel
maps (missing pixels were identified when the raw FITS files
were created).
The pipeline also created a FITS image extension to capture the
signal-to-noise ratio map and another extension to capture the values
used to remove horizontal striping. The calibration steps and files
applied to each raw image are listed in the PROCESSING_HISTORY_TEXT
keyword in the PDS data label.
Data
====
FITS Images and PDS Labels
--------------------------
Each calibrated image is stored as FITS. The primary data unit
contains the two-dimensional CCD image which is followed by two
image extensions that are two-dimensional pixel-by-pixel maps
providing additional information about the CCD image:
- The first extension uses one byte consisting of eight,
single-bit flags to describe the quality of each pixel
in the primary image. The PDS data label defines the
purpose of each single-bit flag.
- The second extension provides a signal-to-noise ratio for
each pixel in the primary image.
- The third extension contains the two columns of DN values that
were subtracted from every non-overclock column in the left
and right halves of the primary image array by the stripe
removal process.
Each FITS file is accompanied by a detached PDS data label. The
EPOXI SIS document provides definitions for the keywords found in
a data label and provides more information about the FITS primary
image and the extensions. Many values in a data label were
extracted from FITS image header keywords which are defined in the
document EPOXI_FITS_KEYWORD_DESC.ASC found in the Deep Impact and
EPOXI documentation dataset, DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V4.0.
File Naming Convention
----------------------
The naming convention for the data labels and FITS files is
MVyymmddhh_eeeeeee_nnn_rr.LBL or FIT where 'MV' identifies the MRI
instrument, yymmddhh provides the UTC year, month, day, and hour at
the mid-point of the observation, eeeeeee is the exposure ID
(OBSERVATION_ID in data labels), nnn provides the image number
(IMAGE_NUMBER in the data labels) within the exposure ID, and
rr identifies the type of reduction:
RR for RADREV data (reversibly calibrated, radiance units)
R for RAD data (partially cleaned RADREV data, radiance units)
Up to 999 individual images or frames can be commanded for one
exposure ID. Therefore, nnn in the file name provides the
sequentially increasing frame number within an exposure ID and
corresponds to IMAGE_NUMBER in the data labels. For example, if 2
frames were commanded for a scan with an exposure ID of 9000341, the
first FITS file name would be MV05070400_9000341_001_RR.FIT and the
last would be MV05070400_9000341_002_RR.FIT.
This convention is the one used by the EPOXI pipeline to construct
data product file names and PRODUCT_IDs. To translate between the
EPOXI and Deep Impact conventions, refer to the
MRI_TRANSLATE_PRODUCT_ID.LBL and MRI_TRANSLATE_PRODUCT_ID.TAB
files located in the DOCUMENT directory of this dataset.
Image Compression
-----------------
All calibrated data products are uncompressed. If an associated
raw data product was compressed on board the flyby spacecraft (and
thus received on the ground and archived as compressed) then the
calibration pipeline used one of four 8-bit lookup tables to
decompress the raw image. For more information, see the EPOXI
Calibration Pipeline Summary document as well as Hampton, et al.
(2005) [HAMPTONETAL2005], Klaasen, et al. (2008) [KLAASENETAL2006]
and Klaasen, et al. (2013) [KLAASENETAL2011].
Image Orientation
-----------------
A true-sky 'as seen by the observer' view is achieved by displaying
the image using the standard FITS convention: the fastest-varying
axis (samples or wavelength) increasing to the right in the display
window and the slowest-varying axis (lines or spatial/along-slit)
increasing to the top. This convention is identified in the data
labels: the SAMPLE_DISPLAY_DIRECTION keyword is set to RIGHT and
LINE_DISPLAY_DIRECTION to UP.
The direction to celestial north, ecliptic north, and the Sun is
provided in data labels by CELESTIAL_NORTH_CLOCK_ANGLE,
ECLIPTIC_NORTH_CLOCK_ANGLE, and SUN_DIRECTION_CLOCK_ANGLE keywords
and are measured clockwise from the top of the image when it is
displayed in the correct orientation as defined by
SAMPLE_DISPLAY_DIRECTION and LINE_DISPLAY_DIRECTION. Please note
the aspect of the North celestial pole in an image can be computed
by adding 90 degrees to the boresight declination given by
DECLINATION in the data labels.
Using this convention for Tempel 1 approach images, ecliptic North
is toward the right, ecliptic East is toward the top, and the Sun
is down. After impact, the Flyby spacecraft came out of shield
mode and turned back to observe at the comet. For lookback images,
ecliptic North is toward the left and both ecliptic East and the
Sun are down.
It is important to note that, in published results about the
encounter, the project elected to rotate MRI images such that
ecliptic North is up, ecliptic East is to the left, and the Sun is
to the right for approach images. This is equivalent to rotating
an image counter-clockwise by 90 degrees with respect to the
convention described above. Published lookback images were rotated
clockwise by 90 degrees with with respect to the convention
described above such that ecliptic North is up and both both
ecliptic East and the Sun are toward the left.
For a comparison of the orientation of MRI flight images with those
from ground-based calibrations as well as those from the High
Resolution Instrument CCD (HRIV) and the Impactor Targeting Sensor
CCD (ITS), see the quadrant nomenclature section in Klaasen, et al.
(2008) [KLAASENETAL2006] and Klaasen, et al. (2013)
[KLAASENETAL2011].
Instrument Alignment
--------------------
For a comparison of the field of view and the relative boresight
alignment of MRI to the High Resolution Instrument Visible CCD
(HRIV) and the slit of the High Resolution IR Imaging Spectrometer
(HRII), see the instrument alignment section of Klaasen, et al.
(2008) [KLAASENETAL2006].
Parameters
==========
Data Units
----------
The calibrated RADREV and RAD image data have units of radiance,
W/(m**2 steradian micron).
Imaging Modes
-------------
A summary of the imaging modes is provided below. For more
information see Hampton, et al. (2005) [HAMPTONETAL2005], Klaasen,
et al. (2008) [KLAASENETAL2006] and Klaasen, et al. (2013)
[KLAASENETAL2011]. All modes are unbinned.
X-Size Y-Size
Mode Name (pix) (pix) Comments
---- ------ ------ ------ ---------------------------------------
1 FF 1024 1024 Full frame, shuttered
2 SF1 512 512 Sub-frame, shuttered
3 SF2S 256 256 Sub-frame, shuttered
4 SF2NS 256 256 Sub-frame, not shuttered
5 SF3S 128 128 Sub-frame, shuttered
6 SF3NS 128 128 Sub-frame, not shuttered
7 SF4O 64 64 Sub-frame, not shuttered
8 SF4NO 64 64 Sub-frame, not shuttered, no overclocks
9 FFD 1024 1024 Full-frame diagnostic, shuttered
Filters
-------
A summary of the characteristics of the MRI filters is provided
below. For more information about the filters including the effective
center wavelengths and the corresponding full-width-half-max values,
refer to Hampton, et al. (2005) [HAMPTONETAL2005], Klaasen, et al.
(2008) [KLAASENETAL2006] and Klaasen, et al. (2013) [KLAASENETAL2011].
Filter Center Width
# Name (nm) (nm) Comments
- ---------- ----- ----- -------------------------------
1 CLEAR1 650 >700 For context; not band limited
2 C2 514 11.8 For C2 in coma
3 GREEN_CONT 526 5.6 For dust in coma
4 RED 750 100 For context
5 IR 950 100 For context; longpass
6 CLEAR6 650 >700 For context; not band limited
7 CN 387 6.2 For CN in coma
8 VIOLET_CONT 345 6.8 For dust in coma
9 OH 309 6.2 For OH in coma
Time- and Geometry-Related Keywords
-----------------------------------
All time-related keywords in the data labels, except
EARTH_OBSERVER_MID_TIME, are based on the clock on board the flyby
spacecraft. EARTH_OBSERVER_MID_TIME provides the UTC when an
Earth-based observer should have been able to see an event recorded
by the instrument.
The SDC pipeline was not able to automatically determine the proper
geometric information for the target of choice in some cases. When
these parameters could not be computed, the corresponding keywords
in the data labels are set to a value of unknown, 'UNK'. Also if
GEOMETRY_QUALITY_FLAG is set to 'BAD' or GEOMETRY_TYPE is set to
'PREDICTED' in the PDS labels, then this indicates the geometry
values may not be accurate and should be used with caution. The
value 'N/A' is used for some geometry-related keywords in the data
labels because these parameters are not applicable.
Observational geometry parameters provided in the data labels were
computed at the epoch specified by the mid-obs UTC, IMAGE_MID_TIME,
in the data labels. The exceptions are the target-to-sun values
evaluated at the time light left the target that reached the
spacecraft at mid-obs time, and the earth-observer-to-target values
evaluated at the time the light that left the target, which reached
the spacecraft at mid-obs time, reached Earth.
Ancillary Data
==============
The timing and geometric parameters included in the data labels and
FITS headers were computed using the final version of the kernel
files archived in the Deep Impact SPICE dataset DI-C-SPICE-6-V1.0.
Coordinate System
=================
Earth Mean Equator and Vernal Equinox of J2000 (EME J2000) is the
inertial reference system used to specify observational geometry
parameters in the data labels.
Software
========
The observations in this dataset are in standard FITS format with PDS
labels, and can be viewed by a number of PDS-provided and commercial
programs. For this reason no special software is provided with this
dataset.
|
| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
The data files in this dataset were reviewed internally by the EPOXI
project.
Review
======
This dataset was peer reviewed and certified for scientific use on
21 March 2014.
Data Coverage and Quality
=========================
There are no unexpected gaps in this dataset. All observations
received on the ground were processed and included in this dataset.
Any dark horizontal patches or stripes through some images indicate
missing data. The image quality map extension identifies where pixels
are missing. If the second most-significant bit of a pixel in the
image quality map is turned on, then data for the corresponding image
pixel is missing. For more information, refer to the EPOXI SIS
document.
Limitations
===========
Timing
------
Geometry-related parameters in the PDS data labels are uncertain at
a level of a few seconds because of a known 2-second discrepancy
between the clocks on board the flyby and impactor spacecraft and
between in-situ data and ground-based observations. After a
detailed analysis of the timing problem in early 2006, improved
self-consistent SPICE kernels were generated by the Deep Impact
project to correlate the spacecraft clocks; there is still a
1-2 second uncertainty between the in-situ data and the ground-
based observations and an uncertainty of about one half of a
second between the clocks on the flyby and impactor spacecraft.
These improved kernels were included in the DI SPICE data set
and were used to calculate the geometric parameters in the PDS
data labels. For more information about this discrepancy, see
the Deep Impact Spacecraft Clock Correlation report,
SCLK_CORRELATION.ASC, provided on the Deep Impact and EPOXI
documentation dataset, DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V4.0.
The EPOXI project plans to generate a complete and highly accurate
set of UTC correlations since launch. This will ultimately result
in a future version of a SCLK that will retroactively change
correlation for **all** Deep Impact and EPOXI data. When this
kernel is available, it will be added to the SPICE data sets for
the two missions and posted on the NAIF/SPICE web site at
http://naif.jpl.nasa.gov/naif/.
VIS Stripes Removal
-------------------
The stripe removal process, also called destriping, as implemented
in the EPOXI calibration pipeline is designed to improve the
quality of HRIV and MRI visible CCD images. The routine works best
on images that have many background pixels, and in most cases,
overall image quality is improved, even if some residual stripes
remain in the image. However, for small 256x256 pixel images, the
stripe removal has a limited field-of-view to determine the stripe
pattern. As a result, the stripe removal process is not complete,
and/or may introduce a small artifact on faint comae. For example,
see image HV05051621_5001649_001. Here, comet Tempel 1 has a modest
brightness with a peak of ~10 DN above the background, with most of
the flux found in first 1st quadrant. The stripes are quite faint
but appropriately removed (the original image can be reconstructed
from the third extension of the file), yet some additional power is
being removed in the first quadrant, coincident with rows that
contain the comet. The residual offset is about 0.5 DN (note that
stripes can be as strong as 4 DN). Overall, the stripe removal
process may not improve the data quality of such small images, and
users are cautioned when analyzing these data.
CCD Horizontal Gap
------------------
Calibration analysis combining Deep Impact and early EPOXI data
determined the two halves of the visible CCDs - the boundary being
the two horizontal central lines 511 and 512 (zero based) - while
physically consistent across the boundary, are 1/6 of a pixel
smaller vertically than a normal row. Therefore, reconstructed
images, which have uniform row spacing, have a 1/3-pixel extension
introduced at the center of the array. Thus for two features on
either side of the midpoint line, the vertical component of the
actual angular separation between those features is one-third of a
pixel less than their measured difference in vertical pixels in the
image. As for all geometric distortions, correction of this
distortion will require resampling of the image and an attendant
loss in spatial resolution. The standard pipeline process does
not perform this correction so as to preserve the best spatial
resolution.
The two 1/6-pixel narrower central rows collect only 5/6 of the
charge of a normal row. This effect is corrected by the flat-field
division for calibrated science images so that the pixels in these
rows have the correct scene radiance assigned to them. However,
point-source or disk-integrated photometric measurements using
aperture photometry areas that include these central rows will be
slightly distorted unless special adjustments are made. For
example, the aperture photometry process for comet 9P/Tempel 1 added
an extra 1/6-pixel worth of signal to the to the pixels in each of
these two rows in the reconstructed, calibrated images as described
in Appendix A of Belton, et al., (2011) [BELTONETAL2011].
Displaying Images
-----------------
Flight software writes an image header over the first 100 bytes of
quadrant A. These image header pixels were included in the calibrated
FITS images. Since the values in these pixels vary dramatically,
it is recommended that the values of the EPOXI:MINIMUM and EPOXI:MAXIMUM
keywords in the data label (or the MINPVAL and MAXPVAL in the FITS
header) be used to scale an image for display because these values
exclude the header bytes as well as the overclock rows and columns
located around the edge of the CCD image. For more information,
see the quadrant nomenclature section of the EPOXI SIS document.
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