| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This volume contains the results of the early cruise images of the
Stardust Navigation Camera. These images are of no clear scientific or
engineering use. They were acquired to ascertain the state of the
camera during a time of successive contaminations and decontamination
actions, as described in detail below. None are considered useful for
calibration of future scientific images, given the nearly continuous
changes in the state of the camera during this period.
A total of 203 images have been acquired by the STARDUST mission as of
29 October 2001. Some of these were taken for geometric and photometric
calibration, but the majority were acquired to check on the state of
the camera during decontamination procedures made necessary by
contamination from unknown sources near the time of launch. As of this
date, the camera is exhibiting near theoretical performance, except for
a filter wheel failure. On February 26, 2001, the filter wheel
suddenly failed to advance on command, remaining in the OpNav (#0)
position. Fortunately OpNav is one of the two broadband filters, and
>95% of the mission can still be accomplished without difficulty. There
simply will be no composite color images of the comet nucleus.
One or more images have been acquired on 31 different dates. A very
brief description of the rationale for each session and the results
obtained follows.
#1 - 3/19/99 A series of 27 images was planned to thoroughly check
out the camera. The spacecraft safed itself after three images, a bias
(zero exposure) frame and two narrow band frames taken at 100 ms
exposure. None showed anything, which seemed strange. (Images 1-3)
#2 - 10/21/99 Various spacecraft software conflicts having been
resolved, it became possible to attempt a new camera checkout, this
time consisting of a bias frame and one image through each of the eight
filters, the latter taken with a 500 ms exposure time. Only the two
broadband images showed stars, and these were weak and very diffuse.
(Images 100-108)
#3 - 2/22/00 Two 200 ms calibration lamp images were taken through
the OpNav filter. These were saturated, proving there was nothing wrong
with the exposure times and the problem was probably more one of
diffusion than absorption. (Images 110-111)
#4 - 2/29/00 Two additional calibration lamp images were acquired
through the OpNav filter, this time with a 20 ms exposure. The
intensity was all there, but the lamp images were severely diffused,
like from the effect of a frost-covered windshield. These images gave
information only about conditions downstream from the lamp, telling
nothing about the condition of the scan mirror or the periscope.
(Images 112-113)
#5 - 5/30/00 Twenty-eight windowed images (351x351 pixels) were
acquired, six of them bias frames and 20 of them through the two wide
band filters. Of those 20, 18 were of the 0 magnitude star Vega and two
of the calibration lamp. The Vega images were taken half through the
periscope and half not, using various exposure times. The periscope
frames showed severe scattered light but no Vega images, very possibly
because the geometrically uncalibrated system missed the star. The
frames off the periscope showed huge diffuse images of Vega near the
edge of the field. The calibration lamp images looked identical to
those taken in February. (Images 114-141)
#6 - 8/8/00 A single windowed bias frame was acquired to check upon
the effects, if any, of a large solar flare the previous week. There
were no obvious effects. (Image 142)
#7 - 8/16/00 It was decided to turn on the CCD heater to see if that
would remove any of the contamination on the optics. Images of the
calibration lamp were taken in pairs, a full frame using the OpNav
filter and a windowed frame using the HiRes (#7) filter, at zero hours,
1, 2, 4, 8, 16, 32, 56, 100, and 143 hours, 20 images in all. The
temperature of the CCD was about 9C during this period. Each image
showed changes, but contamination clearly remained at the conclusion of
the heating. (Images 143-162)
#8 - 8/30/00 A final pair of calibration lamp frames was acquired
after the CCD had cooled back to its normal operating temperature near
-35C. The images were different, but still diffuse. (Images 163-164)
#9 - 9/12/00 Five star fields were obtained using the OpNav filter
and different scan mirror angles. One spacecraft axis was not properly
clamped, so there was smear on all images. (Images 165-169)
#10 - 9/26/00 Sequence #9 was repeated with three identical star
field and two new ones. The images appeared somewhat more diffuse than
those taken pre-heating, but the transmission seemed better, frame
limits being about one magnitude fainter. (Images 170-174)
#11 - 10/17/00 Sixteen frames were taken of the Pleiades (M45) open
cluster to attempt to determine the uniformity of the contamination and
to see if the smaller intrinsic point spread of the HiRes filter would
help us go fainter. Unfortunately there were high drift rates on the
three HiRes images and no conclusion was reached. Contamination across
the frame varied by no more than half a magnitude, but huge scattered
light halos dominated every star image. One compressed frame was
acquired, and it showed the compressor chip was working properly.
(Images 175-190)
#12 - 11/27/00 A single OpNav frame of the calibration lamp was taken
as a baseline for a new heating test. This time, both CCD and scan
mechanism heaters were turned on and brought the CCD up to about 12C
(the spacecraft was now much nearer perihelion). On December 5 the Sun
was turned directly on the CCD radiator for about 30 minutes, bringing
the CCD temperature up to 24C. This was done as part of a scheduled
trajectory correction maneuver. All heaters were turned off on December
18, but navigation studies prevented any further image acquisition
until January. (Image 191)
#13 - 1/5/01 One calibration lamp and four star field frames were
acquired using the OpNav filter and 1000 ms exposures. The cal lamp
frame showed the lamp filament for the first time since launch. The
star frames showed sharper images and reached at least magnitude 9.0.
There was still a very shallow skirt of scattered light around star
images, however, and we were at least one full magnitude from the
performance expected of the camera. (Images 192-196)
#14 - 1/16/01 Some 16 hours after Earth Gravity Assist we acquired 25
frames, five Lunar and two bias frames uncompressed and 16 Lunar and
two bias frames compressed. These were taken at about 100,000 km from
the Moon while flying nearly over its north pole, seeing about two-
thirds front side and one-third back side in a half illuminated image.
The wide band filters gave partially saturated images even at the
minimum possible 5 ms exposure. The narrow band images were sharp but
showed a halo of scattered light, as expected from the results of the
previous sequence. It was intended that these Lunar images be used to
recalibrate the camera. (Images 197-221)
#15 - 2/26/01 A series of 21 compressed full frame images were taken
for the purpose of geometric calibration of the scan mirror. Nineteen
were OpNav images taken at 10 degree intervals from 0 degrees to 180
degrees. Two were HiRes images taken at 80 degrees and 90 degrees,
again to attempt a comparison of performance of OpNav and HiRes
filters. It was immediately obvious that recontamination had occurred
and we were back to the level of the previous Fall as far as scattered
light was concerned. The images were useless for calibration, and any
attempt at photometric calibration from the lunar images taken in
January had been rendered moot. EVRs received, when the filter wheel
was commanded back to its stowed position, said that it had not moved
and still was in the OpNav position. (Images 222-242)
#16 - 3/1/01 Three frames were taken at this time, an uncompressed
cal lamp frame and compressed and uncompressed star fields, the former
to verify the filter wheel position and the later the contamination
state. The first showed that indeed we had not moved from the OpNav
filter position and that the cal lamp filament had once again
disappeared. The later indeed showed renewed contamination. (Images
243-245)
#17 - 3/13/01 A series of nine images had already been planned to
determine exactly where we come off the periscope and the extent of
periscope contamination. A tenth was added as final verification that
we were stuck in the OpNav position (confirmed), and this resulted in
an absolute flight rule forbidding any further attempts to move the
filter wheel, since getting stick in a narrow band filter would
severely damage the mission by causing both a greater flyby distance
and loss of all useful nucleus images. Images of a bright star (Spica)
showed that we were getting about half the expected light through the
periscope, so indeed there is additional contamination on the periscope
mirrors. These also showed that we are fully off the periscope at a 20
degree mirror angle but not 15 degrees and that there was a great deal
of scattered light into the periscope at the spacecraft attitude at
which the images were acquired. (Images 246-255)
#18 - 3/22/01 On this date one cal lamp and one star field were taken
as baseline for a third heating cycle. Immediately following these
exposures, the CCD heater was turned on and the scan mechanism heater
was turned up once again. (Images 256-257)
#19 - 3/27/01 One set of images, cal lamp plus star field, was taken
immediately prior to performing a maneuver to once again point the CCD
radiator at the Sun. This was a hot pair taken at 12C. The camera
reached about 21C, and 45 minutes later, while still at 21C, a further
pair of images was taken. A final pair was taken 12 hours later when
the camera was back at 12C. To everyone's surprise, the first pair,
taken BEFORE the camera radiator was pointed at the Sun, was noisy, as
one would expect with the camera hot, but very clean. There was in fact
no significant difference in the three pairs of images. All looked very
good except for the hot pixels. (Images 258-263)
#20 - 4/2/01 The CCD and scan mechanism heaters were left on
following the March 27 heating cycle. A pair of images was taken during
this and each successive DSN pass. No change was seen. (Images 264-265)
#21 - 4/10/01 Another pair of images was acquired. (Images 266-267)
#22 - 4/18/01 Another pair of images was acquired. (Images 268-269)
#23 - 4/25/01 Another pair of images was acquired, and the heaters
were returned to their normal state on April 29, CCD off and scan
mechanism heating as needed for operation. (Images 270-271)
#24 - 4/30/01 Another pair of images was acquired, this time with the
CCD back down to its normal operating temperature at -36C. Without all
of the hot pixels, we could now see that we were in our cleanest state
since launch, reaching somewhere near 10th magnitude without special
filtering. Since this state was reached immediately after heating to
only 8C, it appears that this recontamination was of a different nature
than the original contamination, perhaps simply water vapor released
when the spacecraft was hottest near perihelion. (Images 272-273)
#25 - 5/7/01 Another pair of images was acquired to check for any
recontamination. (Images 274-275)
#26 - 5/17/01 Another pair of images was acquired to check for any
recontamination. (Images 276-277)
#27 - 5/25/01 Another pair of images was acquired to check for any
recontamination. (Images 278-279)
#28 - 5/31/01 Another pair of images was acquired to check for any
recontamination. (Images 280-281)
#29 - 6/8/01 Sixteen full frame uncompressed images were taken of the
encounter background field with exposures of one, three, and five
seconds, at various mirror settings, and with the spacecraft in
encounter attitude for periscope images, to check for scattered light.
With a 0 degree mirror angle, there was about 200 dn /s of scattered
light in the upper left corner, the worst part of the frame. With a 10
degree mirror angle, there was about 100 dn/s of scattered light in the
upper left corner. At 20 degrees, and clear of the periscope, there was
no scattered light detected. Processing of a five second exposure clear
of the periscope indicated we reached magnitude 11.7 with a signal to
noise ratio of three. There has been no further evidence of
contamination since the third heating cycle began on March 22. (Images
282-297)
#30 - 8/29/01 Two images (298,299) were acquired to check for any
recontamination of the camera and to furnish additional geometric
calibrations. Both proved excellent, showing no new contamination for
the past four months. No additional imaging is planned until the
windowing software patch is available or until standard maintenance
requires a camera status check (in about six months). Useful unwindowed
imaging will not be possible for a year or more, that is, until we have
more power and higher data rate as we begin to approach Sun and Earth
once again. (Images 298-299)
#31 - 10/29/01 In anticipation of a long period with no imaging while
the spacecraft was near aphelion, a final check was made on the state
of the camera. This was used as an opportunity to place the spacecraft
in the attitude relative to the Sun that it will have on approach, if
an engineering readiness test is performed on the asteroid Annefrank in
November 2002, as a check for scattered light. The single 1000 ms image
remained free of significant contamination and showed no scattered
light. (Image 300)
The images on this calibration volume are in standard PDS format. Each
file includes an attached PDS label at the beginning of the file,
followed by a histogram, and ending with the image itself. The PDS
label contains two OBJECT definitions, which describe the storage
requirements for both the histogram and image objects. The label also
describes the circumstances surrounding the collection of the
calibration image. This meta-data is in keyword and value pairs and
each of these keywords is described at the end of this document.
Camera Description
------------------
The camera has a 1024x1024 array as the active portion of the CCD.
The images that are stored on this volume, however, contain more
than just the active portion of the CCD. Each line contains a sync
pattern, a line counter, 12 baseline stabilization pixels, the 1024
pixels from the active portion of the CCD, and finally 8 over-clock
pixels used to measure the quantum efficiency. The number of rows
for each image is always 1024, no matter what compression mode is
used, but the number of columns for each image depends on the
compression mode used.
Compression Modes
-----------------
The NAVCAM images can be either 8-bit or 12-bit data. The 12-bit data
is commonly referred to as 'uncompressed data', while the 8-bit is
referred to as 'compressed data'. This compression is accomplished by
a 12-bit to 8-bit square-root look-up-table compression method, which
is implemented in the hardware of the camera electronics. This
compression is lossy and the estimate of the 12-bit image can be
recovered using the look-up table mentioned in Appendix 3 of the
Calibration Document. Both the image and histogram portions of the
data file require different amounts of storage space, dependent on the
compression mode used.
Pixel storage requirements
--------------------------
In uncompressed mode with 12-bit data, the pixels are expressed in two
bytes, as 16 bits per pixel. The upper nibble of the most significant
byte is always zero for these images. In compressed mode with 8-bit
data, the pixels are expressed in a single byte.
Number of Columns within each Row
---------------------------------
The general form of each line for each image is fixed. The row of
data from the camera can be categorized into five different regions:
1. Sync Pattern Always 2 bytes, with value 0x0000
2. Line Counter Always 2 bytes, values from 0 to 1023
3. 8 BLS pixels *Baseline Stabilization pixels, either 1 or
2 bytes per pixel
4. 1024 image pixels *Either 1 or 2 bytes per pixel
5. 12 over-clock pixels *Used to measure quantum efficiency, either
1 or 2 bytes per pixel
* The pixels are either 1 or 2 bytes per pixel dependent on the
compression mode. Uncompressed, 12-bit images require 2 bytes per
pixel, while compressed 8-bit images require 1 byte per pixel.
For the uncompressed, 12-bit data, each row contains 1046 'pixels' of
data, which is exactly 2092 bytes. This is 2 bytes for the sync, 2
bytes for the line counter, 8 pixels at 2 bytes per pixel, 1024 pixels
at 2 bytes per pixel and, finally, 12 pixels at 2 bytes per pixel. In
equation form:
bytes_per_uncompressed_line = 2 + 2 + 2 * ( 8 + 1024 + 12 ) = 2092
For the compressed, 8-bit data, each row contains 1048 'pixels' of
data, which is exactly 1048 bytes. This is 2 bytes for the sync, 2
bytes for the line counter, 8 pixels at 1 byte per pixel, 1024 pixels
at 1 bytes per pixel and, finally, 12 pixels at 1 bytes per pixel. In
equation form:
bytes_per_compressed_line = 2 + 2 + 1 * ( 8 + 1024 + 12 ) = 1048
Reading with RAW image readers
------------------------------
When using any of the supported PDS readers, this extra data at the
beginning and end of the line is not displayed, but when reading these
images with a raw raster-scan style reader, this extra data at the
beginning and ending of each line must be taken into account.
Values to use when reading images with a RAW readers
----------------------------------------------------
Compression Mode # Rows # Columns Data Type
----------------- ------ --------- ------------------------------
Compressed 1024 1048 BYTE data
Uncompressed 1024 1046 MSB_Unsigned_integer (16-bit)
Finding the offset to the data within the file
----------------------------------------------
When trying to read the histogram or image arrays from the file
using a RAW reader, the reader must first skip all of the information
before the object to be read. As an example, to read the image object
using a raw reader, the reader must first skip the PDS attached header,
as well as the histogram data. To determine the amount of data to
skip, examine two keyword pairs from the attached label.
To advance to the beginning of the histogram data, examine the
following keywords:
RECORD_BYTES = 2092
^IMAGE_HISTOGRAM = 3
The first keyword defines the number of bytes within each record, while
the second keyword indicates at which record the data begins. In this
example, the data starts in record #3. This indicates that 2 other
records contain data prior to the start of the histogram data. To
compute the data offset, account for 2 records of data: in this
example, the offset is (3-1)*2092 = 4184.
To advance to the beginning of the image data, examine the following
keywords:
RECORD_BYTES = 2092
^IMAGE = 11
As in the previous example, the first keyword defines the number of
bytes within each record. The second keyword indicates the record at
which the image data begins. To compute the data offset, follow the
example above:
Offset = ( ^image_histogram - 1 ) * record_bytes.
Ex: Offset = ( 11 - 1) * 2092 = 20920
Flip Required to Achieve ``As Seen By Observer'' Display
--------------------------------------------------------
Since the optical path of the camera includes a mirror and the flight
and image production s/w do not compensate for the flip that this
mirror introduces, the images displayed in normal left-to-right sample,
top-to-bottom line fashion have to be transposed (flipped about left-
top/right-bottom diagonal) in order to appear ``as observer located on
the s/c would see it''.
A Sample PDS Attached Image Label
---------------------------------
PDS_VERSION_ID = PDS3
/*** FILE FORMAT ***/
RECORD_TYPE = FIXED_LENGTH
RECORD_BYTES = 2092
FILE_RECORDS = 1032
/*** POINTERS TO OBJECTS IN FILE ***/
^IMAGE_HISTOGRAM = ('N0164C171.RAW',1)
^IMAGE = ('N0164C171.RAW',9)
/*** GENERAL DATA DESCRIPTION PARAMETERS ***/
MISSION_NAME = 'STARDUST'
SPACECRAFT_NAME = 'STARDUST'
DATA_SET_ID = 'STARDUST-C/E/L-NC-2-EDR-V1.0'
PRODUCT_ID = 'N0164C171.IMG'
PRODUCER_INSTITUTION_NAME = 'JPL/ACT'
PRODUCT_TYPE = 'EDR'
SOFTWARE_NAME = 'ACT DMAPKTDECOM 1.0'
MISSION_PHASE_NAME = 'Cruise 1'
TARGET_NAME = 'N/A'
FRAME_SEQUENCE_NUMBER = 164
/*** TIME PARAMETERS ***/
PRODUCT_CREATION_TIME = 2000-09-15T01:26:31
START_TIME = 2000-08-30T17:30:53.994
STOP_TIME = 'N/A'
SPACECRAFT_CLOCK_START_COUNT = '0652123932:172'
SPACECRAFT_CLOCK_STOP_COUNT = 'N/A'
TIME_FROM_CLOSEST_APPROACH = -1220.075
/*** CAMERA RELATED PARAMETERS ***/
INSTRUMENT_NAME = 'NAVIGATION CAMERA'
INSTRUMENT_HOST_NAME = 'STARDUST'
INSTRUMENT_ID = 'NC'
DATA_STREAM_TYPE = 'CRUISE'
TELEMETRY_MUX_MODE_ID = 1
FILTER_WHEEL_IN_MOTION_MODE_ID = 0
EXPOSURE_ENABLE_MODE_ID = 0
EXPOSURE_DURATION = 150
CCD_HEATER_MODE_ID = 0
SLEEP_MODE_ID = 0
CAL_LAMP_MODE_ID = 1
QUANTIZATION_MODE_ID = 0
FIFO_EMPTY_MODE_ID = 1
FIFO_FULL_MODE_ID = 0
BULB_MODE_ID = 0
FILTER_STEPS = 7
FILTER_PARITY = 0
FILTER_NUMBER = 7
FILTER_NAME = 'HiRes'
CENTER_FILTER_WAVELENGTH = 596.4
FILTER_FWHM = 200
NAVCAM_DIGITAL_TELEMETRY = 16#849ea1b0c0d5e7f7#
SCAN_MIRROR_ANGLE = -0.012817
SCAN_MIRROR_LAST_COMMANDED_VELOCITY = 0
SCAN_MIRROR_MOTOR_MODE_ID = 0
/*** TEMPERATURE PARAMETERS IN ***/
FOCAL_PLANE_TEMPERATURE = 234.713
SCAN_MIRROR_TEMPERATURE = 265.614
NOTE = '
EARTH MEAN EQUATOR AND VERNAL EQUINOX J2000 COORDINATES ARE
THE INTERTIAL REFERENCE SYSTEM USED TO SPECIFY OBSERVATIONAL
GEOMETRY. LATITUDE AND LONGITUDE COORDINATES OF TARGET ARE
GEOCENTRIC. GEOMETRIC PARAMETERS ARE BASED ON BEST AVAILABLE
DATA AT TIME OF PRODUCT CREATION. REFER TO EDR SPICE DATA
BASE FOR THE MOST CURRENT OBSERVATIONAL GEOMETRY DATA.'
/*** LINE-OF-SITE ON CELESTIAL SPHERE: Angles in ***/
RIGHT_ASCENSION = 325.41
DECLINATION = -12.7562
TWIST_ANGLE = 1E+32
RETICLE_POINT_RA = ( 324.357, 323.094, 326.444, 327.744)
RETICLE_POINT_DEC = (-15.0215,-11.7291,-10.4868, -13.763)
EMEJ2000_SC_QUATERNION = ( 0.79995, -0.18296, -0.25495, 0.51148)
/*** TARGET PARAMETERS: Position , Velocity ***/
SC_TARGET_POSITION_VECTOR = ( -1E+32, -1E+32, -1E+32)
SC_TARGET_VELOCITY_VECTOR = ( -1E+32, -1E+32, -1E+32)
TARGET_CENTER_DISTANCE = -1E+32
SUN_TARGET_POSITION_VECTOR = ( -1E+32, -1E+32, -1E+32)
SUN_TARGET_VELOCITY_VECTOR = ( -1E+32, -1E+32, -1E+32)
SUN_TARGET_CENTER_DISTANCE = -1E+32
/*** TARGET WITHIN SENSOR FOV: Angles ***/
CENTER_LATITUDE = -1E+32
CENTER_LONGITUDE = -1E+32
HORIZONTAL_PIXEL_SCALE = -1E+32
VERTICAL_PIXEL_SCALE = -1E+32
SMEAR_MAGNITUDE = 0.0749415
SMEAR_AZIMUTH = 59.2858
RETICLE_POINT_LATITUDE = ( -1E+32, -1E+32, -1E+32, -1E+32)
RETICLE_POINT_LONGITUDE = ( -1E+32, -1E+32, -1E+32, -1E+32)
/*** SPACECRAFT POSITION WITH RESPECT TO BODY ***/
SUB_SPACECRAFT_LATITUDE = -1E+32
SUB_SPACECRAFT_LONGITUDE = -1E+32
SPACECRAFT_ALTITUDE = -1E+32
SUB_SPACECRAFT_AZIMUTH = -1E+32
/*** VIEWING AND LIGHTING GEOMETRY (SUN ON TARGET) ***/
PHASE_ANGLE = -1E+32
INCIDENCE_ANGLE = -1E+32
EMISSION_ANGLE = -1E+32
/*** DESCRIPTION OF OBJECTS CONTAINED IN THE FILE ***/
OBJECT = IMAGE_HISTOGRAM
ITEMS = 4096
DATA_TYPE = MSB_UNSIGNED_INTEGER
ITEM_BITS = 32
END_OBJECT = IMAGE_HISTOGRAM
OBJECT = IMAGE
LINES = 1024
LINE_SAMPLES = 1024
SAMPLE_TYPE = MSB_UNSIGNED_INTEGER
SAMPLE_BITS = 16
SAMPLE_BIT_MASK = 2#0000111111111111#
MAXIMUM = 3994
MINIMUM = 0
LINE_PREFIX_BYTES = 20
LINE_SUFFIX_BYTES = 24
MEAN = 243.533
STANDARD_DEVIATION = 670.976
SATURATED_PIXELS = 0
CHECKSUM = 255362468
OBJECT = WINDOW
WINDOW_DESC = 'HEATING TEST'
TARGET_NAME = 'COLD AGAIN IMAGE'
FIRST_LINE = 336
FIRST_LINE_SAMPLE = 336
LINES = 351
LINE_SAMPLES = 351
END_OBJECT = WINDOW
END_OBJECT = IMAGE
END
General notes regarding label
-----------------------------
* Strings appear in quotes.
* Integers and PDS Times do not take quotes.
* Lists are enclosed within {} type brackets.
* If a field is unknown, 'UNK' may be entered.
* If a field is not applicable, 'N/A' may be entered.
* Fields can spill freely, with or without white space, onto
following lines.
* Not all images contain the WINDOW object as part of the
image object. This subobject is only present when windowed
data is present in the image. Images which are full-frame do not
have the WINDOW subobject.
Definition of Keywords/Values from the PDS Data Dictionary
----------------------------------------------------------
PDS_VERSION_ID The pds_version_id Keywords indicates the
version number of the PDS standards
documents that is valid when a data
product label is created. Values for the
PDS_VERSION_ID are formed by appending
the integer for the latest version number
to the letters 'PDS'. Examples: PDS3,
PDS4.
RECORD_TYPE The record_type keyword indicates the
record format of a file. Note: In the
PDS, when record_type is used in a
detached label file it always describes
its corresponding detached data file, not
the label file itself. The use of
record_type along with other file-related
data elements is fully described in the
PDS Standards Reference.
RECORD_BYTES The record_bytes keyword indicates the
number of bytes in a physical file
record, including record terminators and
separators.
FILE_RECORDS The file_records keyword indicates the
number of physical file records,
including both label records and data
records.
^IMAGE_HISTOGRAM The image_histogram object represents a
pointer to the image histogram. The
value is in 'RECORD_BYTE' units. This
represents the record at which the
histogram data begins. Because of this
fact, account for one less than the
number of records shown. As an example,
if the pointer value is 4, and the bytes
per record is 2092, the image histogram
data starts at (4-1)*2092 = 6276 bytes.
^IMAGE The ^image pointer represents a byte
offset to the image data. The value is
in 'RECORD_BYTE' units. This represents
the record at which the image data
begins. Because of this fact, account for
one less than the number of records
shown. As an example, if the pointer
value is 11, and the bytes per record is
2092, the image histogram data starts at
byte 29020.
MISSION_NAME The mission_name element identifies a
major planetary mission or project. A
given planetary mission may be associated
with one or more spacecraft.
SPACECRAFT_NAME The spacecraft_name element provides the
full, unabbreviated name of a spacecraft.
DATA_SET_ID The data_set_id element is a unique
alphanumeric identifier for a data set or
a data product. The data_set_id value
for a given data set or product is
constructed according to flight project
naming conventions. In most cases the
data_set_id is an abbreviation of the
data_set_name. Example value:
STARDUST-C/E/L-NC-2-EDR-V1.0. Note: In
the PDS, the values for both data_set_id
and data_set_name are constructed
according to standards outlined in the
Standards Reference.
PRODUCT_ID The product_id data element represents a
permanent, unique identifier assigned to
a data product by its producer. Note:
In the PDS, the value assigned to
product_id must be unique within its data
set. This value represents the actual
name of the image file on the archive.
The output directory is also available.
PRODUCER_INSTITUTION_NAME The producer_institution_name element
identifies a university, research center,
NASA center or other institution
associated with the production of a data
set. This would generally be an
institution associated with the element
producer_full_name. In this dataset,
this field has the value 'JPL/ACT',
described as:
JPL = Jet Propulsion Laboratory.
ACT = Applied Coherent Technology Corp
PRODUCT_TYPE The product_type data element identifies
the type or category of a data product
within a data set. Examples: EDR, UDR.
SOFTWARE_NAME The software_name element identifies data
processing software such as a program or
a program library.
MISSION_PHASE_NAME The mission_phase_name element provides
the commonly-used identifier of a mission
phase.
TARGET_NAME The target_name element identifies a
target. The target may be a planet,
satellite, ring, region, feature,
asteroid or comet. See target_type.
FRAME_SEQUENCE_NUMBER The frame_sequence_number element
indicates the location within a cycle at
which a specific frame occurs. Frames
are repeated in a specific order within
each cycle. In this dataset, this value
represents a uniquely sequential
identifier assigned to each image of the
archive.
PRODUCT_CREATION_TIME The product_creation_time element defines
the UTC system format time when a product
was created. Formation rule:
YYYY-MM-DDThh:mm:ss.
START_TIME The start_time element provides the date
and time of the beginning of an event or
observation (whether it be a spacecraft,
ground-based, or system event) in UTC
system format. Formation rule:
YYYY-MM-DDThh:mm:ss.
STOP_TIME The stop_time element provides the date
and time of the end of an observation or
event (whether it be a spacecraft,
ground-based, or system event) in UTC
system format. Formation rule:
YYYY-MM-DDThh:mm:ss.
SPACECRAFT_CLOCK_START_COUNT
The spacecraft_clock_start_count element
provides the value of the spacecraft
clock at the beginning of a time period
of interest.
SPACECRAFT_CLOCK_STOP_COUNT
The spacecraft_clock_stop_count element
provides the value of the spacecraft
clock at the end of a time period of
interest.
TIME_FROM_CLOSEST_APPROACH
The time_from_closest_approach element
provides the time with respect to
periapsis or closest approach.
INSTRUMENT_NAME The instrument_name element provides the
full name of an instrument. Note: that
the associated instrument_id element
provides an abbreviated name or acronym
for the instrument.
INSTRUMENT_HOST_NAME The instrument_host_name element provides
the full name of the host on which an
instrument is based. This host can be
either a spacecraft or an earth base.
Thus, the instrument_host_name element
can contain values which are either
spacecraft_name values or earth_base_name
values.
INSTRUMENT_ID The instrument_id element provides an
abbreviated name or acronym which
identifies an instrument. Note: The
instrument_id is not a unique identifier
for a given instrument. Note also that
the associated instrument_name element
provides the full name of the instrument.
DATA_STREAM_TYPE The data_stream_type element identifies a
particular type of data stream to which
the given data product is related. The
images on this archive will be
categorized as either 'Cruise' or
'Encounter' images, indicating the
configuration of the spacecraft when the
images were acquired.
EXPOSURE_DURATION The exposure_duration element provides
the value of the time interval between
the opening and closing of an instrument
aperture (such as a camera shutter).
TELEMETRY_MUX_MODE_ID The telemetry_mux_mode_id element
indicates that the NAVCAM telemetry
multiplexor has sampled all digital
engineering measurements. This value
should always be 1 by the nature of the
timing of the sampling of the
multiplexor.
FILTER_WHEEL_IN_MOTION_MODE_ID
The filter_wheel_in_motion_mode_id
indicates that the filter wheel is in
motion. Upon completion of the movement
of the filter wheel, this value is set to
a 0.
EXPOSURE_ENABLE_MODE_ID The exposure_enable_mode_id element
indicates that the shutter has been
enabled to open, and if successfully
closed, should have a value of 0.
EXPOSURE_DURATION Exposure duration (integration time) of
the image observation expressed in
milliseconds.
CCD_HEATER_MODE_ID The ccd_heater_mode_id element indicates
if the CCD heater is on, with a value of
1, or off, with a value of 0. This value
is controlled independently by spacecraft
commands.
SLEEP_MODE_ID The sleep_mode_id element indicates if
the camera is in sleep mode, or in a low-
power state. A value of 1 indicates that
sleep mode is enables and a value of 0
indicates that sleep mode is disables.
Once sleep mode has been enabled, it can
only be disabled by cycling power to the
NAVCAM.
CAL_LAMP_MODE_ID The cal_lam_mode_id element provides the
value of the calibration lamp mode at the
time the image was acquired. This value
indicates whether the calibration lamp
was on or off at the time the image was
acquired.
QUANTIZATION_MODE_ID The quantization_mode_id element provides
the identifier for the quantization mode
used when the image was acquired. This
value indicates if the original data was
quantized at the time the data was
acquired. A value of 'off' indicates
that the data was not quantized, while a
value of 'on' indicates that the data was
quantized. In this dataset, this value
indicates that the image was compressed
with a hardware square-root compression
technique prior to transmission.
FIFO_EMPTY_MODE_ID The fifo_empty_mode_id indicates if the
readout FIFO is empty or not. When this
value is set to 1, the FIFO is empty and
when it is 0, the FIFO is not empty.
FIFO_FULL_MODE_ID The fifo_full_mode_id indicates if the
readout FIFO is full or not. When this
value is set to 1, the FIFO is full and
when it is 0, the FIFO is not full. When
the FIFO becomes full, pixel data is
overwritten in the NAVCAM's FIFO. This
value represents the state of the FIFO
just before the new image was taken and
represents the previous image's success.
BULB_MODE_ID The bulb_mode_id element indicates if the
shutter has been commanded open. As long
as this value remains a 1, the shutter
will remain open. This value is
controlled only by spacecraft commands.
When a command is received from the
spacecraft to set the bulb_mode value to
0, the shutter is closed. No image is
acquired as a result of a bulb_mode off
command. This value is used to take
images whose exposure duration must be
longer than 20 seconds.
FILTER_STEPS The filter_steps element indicates how
many filters were traversed to reach the
filter of interest. To move from one
filter to the next takes one second, so a
three step move would take three seconds.
FILTER_PARITY The filter_parity element is an odd
parity bit to allow for identification of
a faulty bit amongst one of the three
bits needed to represent the filter
number.
FILTER_NUMBER The filter_number element provides the
number of an instrument filter through
which an image or measurement was
acquired or which is associated with a
given instrument mode. Note: that the
filter_number is unique, while the
filter_name is not.
FILTER_NAME The filter_name element provides the
commonly-used name of the instrument
filter through which an image or
measurement was acquired or which is
associated with a given instrument mode.
Example values: RED, GREEN. See also
filter_number.
CENTER_FILTER_WAVELENGTH The center_filter_wavelength element
provides the mid_point wavelength value
between the minimum and maximum
instrument filter wavelength values.
FILTER_FWHM The filter_fwhm element provides the
measurement for the Full-width, half-max
value associated with the filter. This
is the width of the filter transmission
curve at the point of half of the maximum
transmission value.
NAVCAM_DIGITAL_TELEMETRY The navcam_digital_telemetry element is
used to indicate the eight bytes returned
from the camera at the completion of the
acquisition of an image. The upper
nibbles of each of the eight bytes should
follow the pattern of 0x89abcdef. This
is a check that can be used to determine
if the camera is functioning properly.
The lower nibbles of each of the eight
bytes were used in determining many of
the other parameters given in the other
columns of data.
SCAN_MIRROR_ANGLE The scan_mirror_angle element indicates
the angle of the scan mirror at the
instant the image was taken. The mirror
sweeps through the plane formed by the
spacecraft X and Z axes. When the mirror
is at 0 degrees, the light path is
essentially from the +X axis. As the
mirror rotates to +90 degrees, the light
path is from the -Z axis. When the
mirror moves on to +180 degrees, the
light path is in the direction of the -X
axis. The range of the mirror is
approximately 0 degrees to +200 degrees.
SCAN_MIRROR_LAST_COMMANDED_VELOCITY
The scan_mirror_last_commanded_velocity
element indicates the last commanded
velocity for the scan mirror. The scan
mirror is not commanded to a position,
but rather is reset to an initial
position and is then commanded at a
specific velocity for a specific amount
of time. The value given here is that
commanded velocity.
SCAN_MIRROR_MOTOR_MODE_ID The scan_mirror_motor_mode_id indicates
if the scan mirror motor is either on or
off. When the value is a 1, the motor is
on. When the value is a 0, the motor is
off.
FOCAL_PLANE_TEMPERATURE The focal_plane_temperature element
provides the temperature of the focal
plane array in degrees Kelvin at the time
the observation was made.
SCAN_MIRROR_TEMPERATURE The scan_mirror_temperature element
provides the temperature of the scan
mirror in degrees Kelvin at the time the
observation was made.
RIGHT_ASCENSION The right_ascension element provides the
right ascension value. Right_ascension is
defined as the arc of the celestial
equator between the vernal equinox and
the point where the hour circle through
the given body intersects the Earth's
mean equator (reckoned eastward).
DECLINATION The declination element provides the
value of an angle, corresponding to
latitude, used to fix position on the
celestial sphere. Declination is
measured positive north and negative
south of the celestial equator, and is
defined relative to a specified reference
period or epoch.
TWIST_ANGLE The twist_angle element provides the
angle of rotation about an optical axis
relative to celestial coordinates. The
RIGHT_ASCENSION, DECLINATION and
TWIST_ANGLE elements define the pointing
direction and orientation of an image or
scan platform.
RETICLE_POINT_RA These parameters refer to the right
ascension of the principal points of the
camera. For the left pixel of the camera
(line 1, sample 1), the upper right pixel
(line 1 , last sample), lower left (last
line, sample 1), and lower right(last
line, last sample).
RETICLE_POINT_DEC These parameters refer to the declination
of the principal points of the camera.
For the left pixel of the camera (line 1,
sample 1), the upper right pixel (line 1,
last sample), lower left (last line,
sample 1), and lower right(last line,
last sample).
EMEJ2000_SC_QUATERNION The emej2000_sc_quaternion element
identifies the quaternion required to
rotate a vector in Earth-Mean-Equator
J2000 coordinates into the spacecraft
frame.
SC_TARGET_POSITION_VECTOR The sc_target_position_vector element
indicates the x-, y-, z- components of
the position vector from observer to
target center expressed in J2000
coordinates, and corrected for light time
and stellar aberration, evaluated at
epoch at which image was taken.
SC_TARGET_VELOCITY_VECTOR The sc_target_velocity_vector element
indicates the x-, y-, z- components of
the velocity vector from observer to
target center expressed in J2000
coordinates, and corrected for light time
and stellar aberration, evaluated at
epoch at which image was taken.
TARGET_CENTER_DISTANCE The target_center_distance element
provides the distance between an
instrument and the center of mass of the
named target.
SUN_TARGET_POSITION_VECTOR The sun_target_position_vector element
indicates the x-, y-, z- components of
the position vector from sun to target
center expressed in J2000 coordinates,
and corrected for light time and stellar
aberration, evaluated at epoch at which
image was taken.
SUN_TARGET_VELOCITY_VECTOR The sun_target_velocity_vector element
indicates the x-, y-, z- components of
the velocity vector from sun to target
center expressed in J2000 coordinates,
and corrected for light time and stellar
aberration, evaluated at epoch at which
image was taken.
SUN_TARGET_CENTER_DISTANCE The sun_target_center_distance element
provides the distance between the sun and
the center of mass of the named target.
CENTER_LATITUDE The center_latitude element provides the
latitude of the surface intercept point
of the boresight of the camera.
CENTER_LONGITUDE The center_longitude element provides the
longitude of the surface intercept point
of the boresight of the camera.
HORIZONTAL_PIXEL_SCALE The horizontal_pixel_scale element
indicates the horizontal picture scale.
VERTICAL_PIXEL_SCALE The vertical_pixel_scale element
indicates the vertical picture scale.
SMEAR_MAGNITUDE The smear_magnitude element indicates how
far an image was smeared during an
exposure.
SMEAR_AZIMUTH The smear_azimuth element indicates the
direction in which an image was smeared.
The values of this angle increment in a
clockwise direction from a horizontal
reference line.
RETICLE_POINT_LATITUDE The reticle_point_latitude element
provides the latitude of the surface
intercept points of the principle points
of the camera, defined as the upper left
pixel of the camera (line 1,sample 1),
the upper right pixel (line 1, last
sample), lower left (last line, sample
1), and lower right (last line, last
sample).
RETICLE_POINT_LONGITUDE The reticle_point_longitude element
provides the longitude of the surface
intercept points of the principle points
of the camera, defined as the upper left
pixel of the camera (line 1, sample 1),
the upper right pixel (line 1, last
sample), lower left (last line, sample
1), and lower right (last line, last
sample).
SUB_SPACECRAFT_LATITUDE The sub_spacecraft_latitude element
provides the latitude of the
sub-spacecraft point. The sub-spacecraft
point is that point on a body which lies
directly beneath the spacecraft.
SUB_SPACECRAFT_LONGITUDE The sub_spacecraft_longitude element
provides the longitude of the
sub-spacecraft point. The sub-spacecraft
point is that point on a body which lies
directly beneath the spacecraft.
SPACECRAFT_ALTITUDE The sub_spacecraft_azimuth element
provides the value of the angle between
the line from the center of an image to
the sub-spacecraft point and a horizontal
reference line (in the image plane)
extending from the image center to the
middle right edge of the image. The
values of this angle increase in a
clockwise direction.
SUB_SPACECRAFT_AZIMUTH The spacecraft_altitude element provides
the distance from the spacecraft to a
reference surface of the target body
measured normal to that surface.
PHASE_ANGLE The phase_angle element provides a
measure of the relationship between the
instrument viewing position and incident
illumination (such as solar light).
Phase_angle is measured at the target; it
is the angle between a vector to the
illumination source and a vector to the
instrument. If not specified, the target
is assumed to be at the center of the
instrument field of view. If
illumination is from behind the
instrument, phase_angle will be small.
INCIDENCE_ANGLE The incidence_angle element provides a
measure of the lighting condition at the
intercept point. Incidence angle is the
angle between the local vertical at the
intercept point (surface) and a vector
from the intercept point to the sun. The
incidence_angle varies from 0 degrees
when the intercept point coincides with
the sub_solar point to 90 degrees when
the intercept point is at the terminator
(i.e., in the shadowed or dark portion of
the target body). Thus, higher values
to the middle right edge of the image.
The values of this angle increase in a
clockwise direction. of incidence_angle
indicate the existence of a greater
number of surface shadows.
EMISSION_ANGLE The emission_angle element provides the
value of the angle between the surface
normal vector at the intercept point and
a vector from the intercept point to the
spacecraft. The emission_angle varies
from 0 degrees when the spacecraft is
viewing the sub-spacecraft point (nadir
viewing) to 90 degrees when the intercept
is tangent to the surface of the target
body. Thus, higher values of
emission_angle indicate more oblique
viewing of the target. Values in the
range of 90 to 180 degrees are possible
for ring data.
OBJECT = IMAGE_HISTOGRAM The histogram object is a sequence of
numeric values that provides the number
of occurrences of a data value or a range
of data values in a data object. The
number of items in a histogram will
normally be equal to the number of
distinct values allowed in a field of the
data object. (For example, an 8-bit
integer field can have 256 values.
This would result in a 256-item
histogram.) Histograms may be used to
bin data, in which case an offset and
scaling factor indicate the dynamic range
of the data represented. The following
equation allows the calculation of the
range of each 'bin' in the histogram.
'bin lower boundary' = ('bin element'
* scaling_factor) + offset.
ITEMS The items element defines the number of
multiple, identical occurrences of an
single object, such as a column. See
also: repetitions. Note: In the PDS,
the data element ITEMS is used for
multiple occurrences of a single object,
such as a column. REPETITIONS is used
for multiple occurrences of a repeating
group of objects, such as a container.
For a fuller description of the use of
these data elements, please refer to the
Standards Reference.
DATA_TYPE The data_type element supplies the
internal representation and/or
mathematical properties of a value being
stored. See also: bit_data_type,
general_data_type. Note: In the PDS,
users may find a bit-level description of
each data type in the Standards Reference
document.
ITEM_BITS The item_bits element indicates the
number of bits allocated for a particular
bit data item. Note: In the PDS, the
item_bits element is used when the items
element specifies multiple occurrences of
an implied item within a BIT_COLUMN
object definition.
END_OBJECT The end_object element terminates the
object
OBJECT = IMAGE A regular array of sample values. Image
objects are normally processed with
special display tools to produce a visual
representation of the sample values. This
is done by assigning brightness levels or
display colors to the various sample
values. Images are composed of LINES and
SAMPLES. They may contain multiple
bands, in one of several storage orders.
Note: Additional engineering values may
be prepended or appended to each LINE of
an image, and are stored as concatenated
TABLE objects, which must be named
LINE_PREFIX and LINE_SUFFIX. IMAGE
objects may be associated with other
objects, including HISTOGRAMs, PALETTEs,
HISTORY, and TABLEs which contain
statistics, display parameters,
engineering values, or other ancillary
data.
LINES The lines element indicates the total
number of data instances along the
vertical axis of an image. Note: In PDS
label convention, the number of lines is
stored in a 32-bit integer field. The
minimum value of 0 indicates no data
received.
LINE_SAMPLES The line_samples element indicates the
total number of data instances along the
horizontal axis of an image.
SAMPLE_TYPE The sample_type element indicates the
data storage representation of sample
value.
SAMPLE_BITS The sample_bits element indicates the
stored number of bits, or units of binary
information, contained in a line_sample
value.
SAMPLE_BIT_MASK The sample_bit_mask element identifies
the active bits in a sample. Note: In
the PDS, the domain of sample_bit_mask is
dependent upon the currently-described
value in the sample_bits element and only
applies to integer values. For an 8-bit
sample where all bits are active the
sample_bit_mask would be 2#11111111#.
MAXIMUM The maximum element indicates the largest
value occurring in a given instance of
the data object.
MINIMUM The minimum element indicates the
smallest value occurring in a given
instance of the data object.
LINE_PREFIX_BYTES The line_prefix_bytes element indicates
the number of non-image bytes at the
beginning of each line. The value must
represent an integral number of bytes.
LINE_SUFFIX_BYTES The line_suffix_bytes element indicates
the number of non-image bytes at the end
of each line. This value must be an
integral number of bytes.
MEAN The mean element provides the average of
the DN values in the image array.
STANDARD_DEVIATION The standard_deviation element provides
the standard deviation of the DN values
in the image array.
SATURATED_PIXELS The saturated_pixels element provides a
count of the number of pixels in the
array which at the maximum DN value. For
this dataset, the non-quantized data has
a maximum value of 4095, while the
quantized data has a maximum value of
255.
OBJECT = WINDOW This object is a subobject of the image
object and indicates that this image
contains only a small portion of the
original image. The small portion was
transmitted to the ground, most likely,
in an attempt to conserve bandwidth. The
windowed data allows for the inspection
of certain conditions on the spacecraft
without the need to transmit the entire
image to the ground.
WINDOW_DESC The window_desc value is the description
of the windowed data. It attempts to
describe the circumstances around which
this image data was collected.
TARGET_NAME The target_name element attempts to
describe the item that was being observed
at the time the image was acquired.
FIRST_LINE The first_line element indicates the
first line where valid data begins in the
image. The full image was first padded
with zeros and then this window of data
was overlaid, forming an image of normal
dimensions.
FIRST_LINE_SAMPLE The first_line_sample element indicates
the leftmost column that contains valid
data. This value, paired with the
first_line element create the
upper-leftmost pixel of valid image data.
LINES The lines element indicates the number of
rows of image data associated with this
window.
LINE_SAMPLES The line_samples element indicates the
number of columns of image data
associated with this window.
END_OBJECT The end_object element terminates the
object.
CHECKSUM The checksum element represents an
unsigned 32-bit sum of all data values in
a data object.
END End of the PDS Label.
Contact Information
===================
For any questions regarding the data format of the archive,
contact:
Christopher Hash
Applied Coherent Technology Corp
112 Elden Street, Suite K
Herndon, VA 20170
(703) 742-0294
chash@actgate.com
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