| DATA_SET_DESCRIPTION |
This data set description was provided by Stephanie McLaughlin and
Dennis Wellnitz, University of Maryland, who participated in
the ground calibration tests of the Deep Impact instruments.
Data Set Overview
=================
This data set contains image and temperature data acquired during the
preflight thermal-vacuum test (TV4) of High Resolution Instrument's
Infrared Spectrometer (HRII) and Visible CCD (HRIV) and the Medium
Resolution Instrument's Visible CCD (MRI) for Deep Impact. The
experiments performed during TV4 were designed by the Ball Aerospace
team with input from the Deep Impact science team. TV4 was conducted
by Don Hampton of Ball Aerospace. Several science team members were
present at all times to assist with the experiments and perform
real-time analysis of the data.
The main objective of TV4 was to obtain calibration data for all three
instruments on the Flyby spacecraft at the 140K temperature range for
the HRI optics, warmer than TV2 where the lowest nominal temperature
was 130K. The warmer operating temperature of the IR focal plane
array (FPA) caused bad pixels to bloom in the HRII instrument.
Also, during TV4, several calibration experiments were performed
for the HRII instrument, which had a light-reduction filter
inserted into the middle of the spectrometer's slit after TV2 when
it was determined that the HRII instrument would overexpose the
nucleus of the comet during encounter:
- Perform tests at the nominal operating temperatures of 130K
for the HRI optics and 106K for the IR FPA.
- Determine best focus at the operating temperatures.
- Obtain flat fields from various blackbody sources to measure
the response of the FPA at different wavelengths.
- Determine the non-linearity of the FPA.
- Activate the internal calibration lamp.
- Check for stray light.
- Check for spectral motion caused by motion of the HRIV filter
wheel.
- Check adjustments made to the FPA spectral and spatial
registrations based on TV1 results.
- Check the spatial and spectral dispersion of the FPA.
Also, during TV4, several calibration experiments were performed
for the HRIV and MRI instruments:
- Check focus.
- Check co-alignment and co-focus with the HRII instrument.
- Check registration of the parallel overclock columns and
the serial overclock rows.
- Test the photo-response of the CCD by using several calibrated
blackbody sources and obtain flats.
- Measure dark current as the CCD cools.
- Measure bias.
To meet these objectives, the entire instrument platform for the
Flyby spacecraft was placed inside the Rambo thermal-vacuum
chamber. A test bench was setup outside the chamber to direct
light from an external source through the main window of the
chamber. The chamber was also equipped with a side window made
of Zinc-Selenide to simulate the window of the Ball 8 chamber
that was used during TV2.
TV4 activities are summarized in the following chart.
Avg Temperatures(K)
Date/(DOY) FPA Prism CCD Tests
---------- -------------------- ---------------------------------
2003-02-23 304 305 306 Warm functional tests of all 3
(054) instruments
2003-02-24 304 305 306 Warm functional tests of all 3
(055) instruments
2003-02-25 304 305 306 Warm functional tests of all 3
(056) instruments
HRIV: Warm focus
2003-02-26 ~282 ~281 ~291 Begin cooldown; Functional tests
(057) HRIV: Focus, Dark current
MRI: Dark current
2003-02-27 ~242 ~240 ~253 Continue cooldown
(058) HRII: Test IR delay procedure
HRIV: Dark current
MRI: Dark current, Linearity,
Flats, Focus,
2003-02-28 ~150 ~166 ~185 Continue cooldown
(059) HRIV: Dark current
MRI: Dark current
2003-03-01 ~109 ~142 ~165 Continue cooldown
(060) HRII: Test light-reduction filter,
Dark current, Flats, Argon source
HRIV: Bias, Darks
MRI: Bias, Darks, Latent image,
Internal stimulator, Focus
2003-03-02 ~106 ~140 ~170 Cold
(061) HRII: Light-reduction filter tests
HRIV: Flats, Ambient light, Bias
MRI: Flats, Ambient light, Bias
2003-03-03 ~106 ~140 ~173 HRIV: Co-boresight with MRI, Focus
(062)
MRI: Focus, Flats, Alignment
2003-03-04 ~106 ~140 ~170 MRI: Focus, Flats, Alignment
(063)
2003-03-05 ~106 ~140 ~172 HRII: Ambient light
(064) HRIV: Focus, Latent image, Flats
Shutter block test, Bias
MRI: Imaging
2003-03-06 ~105 ~139 ~168 HRII: Calibration lamp, Argon and
(065) Krypton sources, Co-focus
with HRIV, Light-reduction filter
tests, Flats, Ambient light, Darks
HRIV: Internal stimulator, Bias, Flats
MRI: Flats
2003-03-07 ~106 ~139 ~172 Encounter sequence for all 3
(066) instruments
HRII: IR delay tests, Flats,
CO, CH4, and N2 gas cells, Darks,
Linearity, Boresight with respect
to HRIV
HRIV: HRII boresight
2003-03-08 ~104 ~139 ~168 No data taken
(067)
2003-03-09 ~104 ~139 ~168 Encounter sequence for all 3
(068) instruments
2003-03-10 ~106 ~144 ~180 Encounter sequence for all 3
(069) instruments
HRII: Image test targets
MRI: Image test targets
2003-03-11 ~134 ~160 ~185 HRIV: Warm imaging
(070) MRI: Focus
2003-03-12 ~241 ~244 ~254 MRI: Warm imaging
(071)
For more information about the mission, the HRI and MRI instruments,
and the anticipated flight data, see A'Hearn, et al. (2005)
[AHEARNETAL2005], Hampton, et al. (2005) [HAMPTONETAL2005], and
Klaasen, et al. (2005) [KLAASENETAL2005].
Parameters
==========
HRII
-----
The HRII spectral image data are in units of raw data numbers.
For TV4, all seven of the HRII's image modes were tested:
Image MinExp X-Size Y-Size #Images
Mode# (sec) (pix) (pix) Output Binning Comments
----- ------ ------ ------ ------- ------- ----------------------
1 2.862 512 256 1 2x2
2 1.432 512 126 1 2x2
3 0.717 512 64 1 2x2
4 2.861 1024 512 1 1x1
5 2.865 512 256 1 2x2
6 1.432 1024 512 2 1x1 Reset then data frame
7 2.864 1024 512 1 1x1 Memory check mode
In this table, MinExp is the frame-to-frame minimum exposure times,
X-Size is spectral dimension and Y-Size is spatial dimension of the
FPA. For all image modes except 6, the reset frame is automatically
subtracted, on-chip, from the data frame and the result is output.
For more information about the image modes, see Hampton, et. al (2005)
[HAMPTONETAL2005].
HRIV/MRI
--------
The HRIV and MRI image data are in units of raw data numbers.
The following image modes were defined and tested during TV4:
Image MinExp X-Size Y-Size
Mode# (ms) (pix) (pix) Binning Comments
----- ------ ------ ------ ------- -------------------------
1 3.5 1024 1024 1x1 Shuttered
2 3.5 512 512 1x1 Shuttered
3 3.5 256 256 1x1 Shuttered
4 217.8 256 256 1x1 Not shuttered
5 3.5 128 128 1x1 Shuttered
6 98.4 128 128 1x1 Not shuttered
7 47.4 64 64 1x1 Not shuttered
8 47.4 64 64 1x1 Not shuttered,no overscan
9 3.5 1024 1024 1x1 Shuttered; diagnostic
In this table, MinExp is the minimum exposure time and the term
shuttered means the light blocker in the HRIV or MRI instrument
is always used (opened and closed). For all modes, additional
exposure time can be commanded. For unshuttered modes, a delay time
(duration to wait before the start of the CCD readout) can also be
commanded. For more information about the image modes, see
Hampton, et. al (2005) [HAMPTONETAL2005].
Please note that the results from TV2 indicated the need for
additional image modes with shorter minimum exposure times.
Four new image modes were defined and implemented for all of the
Deep Impact CCDs after TV2.
Data
====
Images
------
The data are in the form of FITS files with attached FITS headers
and detached PDS labels. One data files contains one HRII, HRIV
or MRI image. The fastest-varying axis is considered the X axis and
the slowest-varying, the Y axis. TV4 data filenames have this format:
Iyymmdd_hhmmss_sss_x.FIT where the 'yymmdd_hhmmss_sss' string the date,
time and subseconds stamp provided by the ground-support computer
when it stored the original data file. The clock on the ground-support
computer was set to local Mountain time. The 'x' string is valued with
'A' for HRIV or MRI data, and 'B' for HRII data. After TV2,
the ground-support computer was modified to store the reset and data
frames for HRII image mode 6 into two separate data files with unique
time stamps; the reset frame was store first, then the data frame.
For TV4, the ground-support computer stored data files in a native
image format, called 'IMG'. The raw data numbers were 14-bit and
and left justified. A 100-byte image header was pre-pended to each
data array. The 'IMG' data were converted to FITS at the Deep Impact
Science Data Center (SDC) at Cornell University, using algorithms
developed by Ball Aerospace for testing of the instruments and to
allow real-time analysis of data during thermal-vacuum tests.
During the conversion, raw data numbers were right justified to
give the actual, true data numbers. Data in the 100-byte image
header are captured in the FITS header.
After TV2, the Field Programmable Gate Arrays (FPGA) for each of
the CCDs was adjusted so that the columns of serial overclocks
and several rows of parallel overclocks would be correctly
located around the edges of the CCD array.
During TV4, the amplifier gains for the IR FPA were not correct.
This caused the right side of the array (columns 513-1014) to have
a bias about 2000 DN (data number) greater than the left side fo the
array (columns 1-512). Amplifier gains were corrected after TV4.
It is important to note that the higher IR FPA temperature during
TV4 (106K) caused bad pixels to bloom noticeably when compared to
data from TV2, when IR FPA temperatures range was about 86-90K.
Instrument Temperatures
-----------------------
The instrument temperatures found in the PDS labels were extracted
from the temperature keywords in the FITS headers. During TV4,
ground-support equipment correctly recorded temperatures in the
image headers. As a check, temperatures of various components of the
HRII/HRIV and MRI instruments were also recorded every 5 minutes by
two thermister monitors (computers). Temperature data, in fixed-width
ASCII table format, are available in the data directory. There is
one table of HRII/HRIV temperatures and one table of MRI. Time
stamps in the temperature file are are based on local Mountain time
and are within several minutes of the time stamps in the FITS
filenames. Temperatures found in the tables or the PDS labels can be
used for analysis
It is important to note that the IR FPA temperatures recorded by the
thermister monitor were adjusted by -3.26K before being stored in the
temperature table. After thermal-vacuum 4 (TV4), Ball Aerospace
personnel analyzed all IR FPA temperatures and determined the
temperatures recorded by the monitor needed to be adjusted by -3.26K
because the cable connected to this temperature point included about
18 inches of manganin wire which resulted in higher temperature
measurements due to its higher electrical resistance.
.
Ancillary Data
==============
The DOCUMENT directory provides the HRII/HRIV and MRI image
logs recorded during TV4. The logs contain an entry for each image
acquired during TV4 and include image parameters such as mode and
experiment type. The logs include a brief description of each type
of experiment performed during TV4 and a summary of the experiments
performed on each test date.
The DOCUMENT directory also provides daily reports written by the
test leaders and distributed to the test team and the science
team. The reports describe in detail the test activities as well
problems and successes encountered during TV4.
The DOCUMENT directory includes the local PDS data dictionary used
to produce the labels as well as sample IDL code used to read
and extract temperatures from the TV4 HRII/HRIV temperature table.
Media/Format
============
This data set is released as a logical data volume.
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