| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains raw 9P/Tempel 1 and science calibration images
acquired by the Deep Impact Medium Resolution Instrument Visible CCD
(MRI) during the 9P encounter phase of the mission.
The 9P/Tempel 1 data are described in 'Deep Imact: The Anticipated
Flight Data' by Klaasen, et al. (2005) [KLAASENTAL2005]. For more
details about the images taken around impact, refer to the MRI
encounter data summary document which provides a log of the exposures
taken from 28 hours before impact through lookback.
The science calibration images are described in the 'Deep Impact
In-Flight Calibration Summary' document and are also discussed in the
'Deep Impact: Anticipated Flight Data' paper by Klaasen, et al. (2005)
[KLAASENETAL2005]. Calibration targets included the 16 Cyg A,
47 Tuc, Achernar, Beta Hyi, Canopus, Sirius, Vega, HD 60753, HD 79447,
NGC 3114, NGC 7027, an internal calibration (stimulator) lamp, and
dark frames. For a detailed discussion of how the instrument was
calibrated, see 'Deep Impact Instrument Calibration' by Klaasen, et
al. (2006) [KLAASENETAL2006].
A list of the comet and the science calibration 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
2005-05-10 130 5100000 5300023 May Science Cal
2005-05-11 131 5400000 5600000 May Science Cal
2005-05-12 132 5700000 5800009 May Science Cal
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
5910000 5913008 VIS LUT Upload Test
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
2005-06-07 158 6100000 6100010 June Science Cal
2005-06-08 159 6400000 6500025 June Science Cal
2005-06-09 160 6500026 6500037 June Science Cal
2005-06-10 161 6700000 6800009 June Science Cal
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
8700000 8800050 Pre-impact Science Mini-Cal Test
6001400 6001411 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 8100140 Daily Comet Imaging
2005-06-29 180 8100165 8300011 Daily Comet Imaging
2005-06-30 181 8400042 8400482 Daily Comet Imaging
2005-07-01 182 8400561 8500437 Daily Comet Imaging
2005-07-02 183 8500477 8600167 Daily Comet Imaging
8700000 8800179 Pre-impact Science Mini-Cal
2005-07-03 184 9000003 9000246 Continuous Comet Imaging
9000250 9000263 Pre-impact Stim and Dark Cal
9000264 9000340 Continuous Comet Imaging
2005-07-04 185 9000341 9000908 Continuous Comet Imaging
9000909 9001067 Impact Imaging
9010000 9080000 Lookback Imaging
2005-07-05 186 9080000 9120000 Lookback Imaging
2005-07-06 187 9120000 9150017 Lookback Imaging
7100000 7100007 Post-encounter Science Cal
2005-07-07 188 7100008 7200000 Post-encounter Science Cal
2005-07-08 189 7200001 7200028 Post-encounter Science Cal
2005-07-09 190 7300000 7400001 Post-encounter Science Cal
Essential Reading
-----------------
The following documents, located on the Deep Impact Documentation
volume, DIDOC_0001, are essential for the understanding and
interpretation of this data set:
ANTICIPATED_FLIGHT_DATA.* : Anticipated flight data by Klaasen,
et al. (2005) [KLAASENTAL2005]
MRI_ENCOUNTER_DATA_SUMMARY.* : Image log from 28 hours before
impact through lookback
INFLIGHT_CALIBRATION_SUMMARY.* : Summary of in-flight calibrations
CALIBRATION_DOC.* : Instrument calibration by Klaasen,
et al. (2006) [KLAASENETAL2006]
INSTRUMENTS_HAMPTON.* : Instrument paper by Hampton, et al.
(2005) [HAMPTONETAL2005]
MISSION_OVERVIEW_AHEARN.* : Mission overview by A'Hearn, et al.
(2005) [AHEARNETAL2005B]
SCLK_CORRELATION.* : Discussion of the discrepancy
between the spacecraft clocks and
UTC
AIDC_FLIGHT_HRIV_MRI_ITS.* : Description of the data set and
definitions of label keywords
Related Data Sets
-----------------
The following PDS data sets are related to this one:
DIF-CAL-MRI-2-9P-CRUISE-V1.0 : Raw MRI cruise calib data
DIF-C-MRI-3/4-9P-ENCOUNTER-V1.0 : Reduced MRI encounter data
DIF-CAL-HRII/HRIV/MRI-2-GROUND-TV4-V1.0 : HRIV pre-flight calib data
DI-C-SPICE-6-V1.0 : SPICE kernels
Processing
==========
The uncompressed and compressed FITS images in this data set were
created by the Deep Impact Science Data Center (SDC) at Cornell
University and were assembled from raw telemetry packets sent down by
the flyby spacecraft. Information from the embedded spacecraft header
(the first 100 bytes of an uncompressed or 50 bytes of a compressed
image) was extracted and stored in the primary FITS header. Geometric
parameters were computed using the best available SPICE kernels and
the results were also stored in the FITS header. If telemetry packets
were missing, the corresponding pixels were flagged as missing in the
quality map included as a FITS 'IMAGE' extension. The image quality
map was described in the calibration pipeline section of the 'Deep
Impact Instrument Calibration' paper by Klaasen, et al. (2006)
[KLAASENETAL2006]. The SDC did not apply any type of correction or
decompression algorithm to the raw data.
Applied Coherent Technology Corporation in Herndon, VA, produced the
PDS data labels by extracting parameters from the FITS headers.
Data
====
CCD Images
----------
The two-dimensional, visible CCD images in this data set are in
FITS format. The primary data array contains the CCD image and
is followed by an image extension that contains a pixel-by-pixel
quality map. Each FITS file is accompanied by a detached PDS label.
Compression
-----------
This data set contains compressed and uncompressed raw FITS images,
that is, data as they were received on the ground. Data compression
was performed on board the spacecraft using a set of four lossy
lookup tables. A compressed FITS image consisted of 14-bit values
compressed and stored as a one-byte pixel. An uncompressed FITS
image consisted of 14-bit pixels stored as two bytes. The
COMPRESSED_IMAGE_VALUE in the data label indicates if an raw image
is compressed or uncompressed. The COMPRESSOR_ID identifies the
lookup table that was used to compress an image.
The calibration pipeline decompressed raw images. For information
about data compression, refer to 'An Overview of the Instrument
Suite for the Deep Impact Mission' by Hampton, et al. (2005)
[HAMPTONETAL2005] or the instrument calibration paper by Klaasen,
et al. (2006) [KLAASENETAL2006].
Target Name and Description
---------------------------
The TARGET_NAME keyword in the data labels was set to the intended
target, either '9P/Tempel 1' or 'Calibration'. The TARGET_DESC
keyword provides the name of the specific calibration target,
such as 'Dark'.
True-Sky ''As Seen By Observer'' Display
----------------------------------------
A true-sky view is achieved by displaying the image using the
standard FITS convention: the fastest-varying axis (samples)
increasing to the right in the display window and the slowest-
varying axis increasing to the top. This convention is also
defined in the image labels:
SAMPLE_DISPLAY_DIRECTION = 'RIGHT'
LINE_DISPLAY_DIRECTION = 'UP'
This topic is discussed in detail in the 'Quadrant Nomenclature'
section of the 'Deep Impact Instrument Calibration' document.
The direction to Celestial North and Ecliptic North, measured
clockwise from the top of the displayed image, is provided in PDS
labels by CELESTIAL_NORTH_CLOCK_ANGLE and
SOLAR_NORTH_POLE_CLOCK_ANGLE, both of which assume the correct
display defined by SAMPLE_DISPLAY_DIRECTION and
LINE_DISPLAY_DIRECTION.
File Naming Convention
----------------------
The naming convention for the data labels and FITS files is
MVcccccccccc_eeeeeee_nnn.LBL or FIT where cccccccccc is the
spacecraft clock count at the mid-point of the observation, eeeeeee
is the exposure ID (OBSERVATION_ID in data labels). Up to 999
individual images could be commanded for one exposure ID.
Therefore, nnn in the file name provides the sequentially increasing
image number within an exposure ID corresponding to IMAGE_NUMBER in
the data labels. For example, if two images were commanded for
exposure ID 9000022, the two FITS files names would be
MV0173709840_9000022_001.FIT and MV0173709840_9000022_002.FIT.
Parameters
==========
Data Units
----------
Raw image data are in units of raw data numbers.
Imaging Modes and Filters
------------------------
For descriptions of the imaging modes and filters, please see
the Deep Impact instrument paper by Hampton, et al. (2005)
[HAMPTONETAL2005].
Most image modes had a set of bias overclock rows and columns,
located around the edges of the image array. All overclock pixels
were excluded from the calculation of the values for MINIMUM,
MAXIMUM, MEDIAN, and STANDARD_DEVIATION in the data labels.
Time-Related Keywords
---------------------
All time-related keywords in the data labels, except
EARTH_RECEIVED_TIME, are based on the clock on board the flyby
spacecraft. EARTH_RECEIVED_TIME provides the UTC when an
Earth-based observer should be able to see an event recorded by
the instrument.
The TIME_FROM_IMPACT_VALUE keyword in the data labels was based
on the estimated impact time at the flyby spacecraft of UTC
05:44:35.821 on 4 Jul 2005.
Geometry-Related Keywords
-------------------------
The SDC attempted to calculate geometric parameters relating to
the target only when it was within several fields of view of the
instrument boresight. When these parameters could not be
calculated, the corresponding keywords in the PDS data labels were
set to a value of unknown (UNK). Also, geometry-related keywords
for calibration targets such as Canopus were set to UNK.
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. The Deep Impact
project generated self-consistent SPICE kernels, outside of NAIF, to
help account for the discrepancy. The November 2005 version of
these kernels was used to calculate the image times and geometric
information in PDS data labels. After further analysis of the
timing problem in early 2006, improved self-consistent SPICE kernels
were generated by the Deep Impact project. These kernels are
included in the DI SPICE data set. For more information about
this discrepancy, please see the spacecraft clock correlation
document included on the Deep Impact document volume.
Ancillary Data
==============
Geometric parameters included in the data labels were computed using
the November 2005 version of the SPICE data. These were the best
available data at the time of image creation. Since image creation,
some SPICE data have been improved, and these are archived in the
Deep Impact SPICE data set.
Coordinate System
=================
Earth Mean Equator and Vernal Equinox of J2000 (EME J2000) was the
inertial reference system used to specify observational geometry
parameters in the data labels.
Geometric parameters provided in the data labels were computed at
the epoch specified by MID_IMAGE_TIME, except for the target-to-sun
and earth-observer-to-target parameters. Target-to-sun values were
calculated for the time when the light left the sun while
earth-observer-to-target were calculated for the time when the light
left the target.
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