Data Set Information
|
| DATA_SET_NAME |
DAWN FC2 RAW (EDR) CERES IMAGES V1.0
|
| DATA_SET_ID |
DAWN-A-FC2-2-EDR-CERES-IMAGES-V1.0
|
| NSSDC_DATA_SET_ID |
|
| DATA_SET_TERSE_DESCRIPTION |
Experiment data records for Framing
Camera 2 on Dawn during the Ceres
Encounter Phases
|
| DATA_SET_DESCRIPTION |
Data set overview
================
This data set includes the Experiment Data Record (EDR) version of all
available images acquired during the Ceres Prime Mission (Approach,
Transfer to Survey, Survey, HAMO, and LAMO),and extended missions 1
(XMO1, XMO2, XMO3, XMO4) and 2 (XMO6, XMO7). In addition to the imagery,
ancillary information is stored within the image headers. Calibration
files needed for further processing are archived as a separate data set.
This data set is the primary record of image data as it was received
on Earth. The images in this data set have not been processed in any
way other than by decompressing, extracting header information, and
generating and attaching PDS labels.
This data set includes individual dark and calibration lamp images.
These images are the inputs to the composite calibration files which
are needed for further processing of the raw images. The composite
calibration files are archived as a separate data set.
For more information on the contents and organization of the volume
set refer to the aareadme.txt file located in the root directory of
the data volumes.
Parameters
==========
Compression: FC images may optionally be compressed by wavelet
transformation.
Wavelet compression: Images may be integer or floating point wavelet
transform-compressed in the DPU. The integer approach produces lossless
compression, while the floating point can induce distortions of +/-1 DN.
The encoding of the wavelets ensures that any length of the data
starting at the beginning can be decoded, thus allowing to compress
further by discarding the trailing part.
Windowing: In order to manage downlink resources, up to 10 portions
of the image can be selected in the DPU and downlinked as subframes.
The subframes are allowed to overlap. During EDR construction each
subframe is stored separately and also mosaicked into the original
image.
Exposure Control: The exposure time of FC images is set
by command for each image.
Pointing: The Framing Cameras are fix mounted onto the Dawn Instrument
deck, with the nominal alignment of the optical axis with the +Z axis of
the spacecraft. Deviations from the nominal are documented in the
calibration data.
Filter selection: The FC has 8 filters at its disposal, numbered from F1
to F8. F1 is a broadband (clear) filter, sensitive in the wavelength
interval from 400 to 1100 nm peaking at 700 nm. The narrow-band color
filters are of the interference type, and have wavelengths ranging from
430 to 980 nm.
Processing
==========
An FC image downlinked by the spacecraft unpacks into a succession of
one or more compressed image subframes with an attached PDS headers
containing housekeeping items that include full status of the instrument
hardware, software configuration, temperature, voltage and current
readings.
The data in one EDR consists of one or more reconstructed image frames,
with the accompanying header translated into text format in the label.
The dimensions and location (pixel coordinates) of each frame are
included for proper further processing. Each frame is formatted into
one file (suffix *.IMG), with an attached label.
Subframes are retained as separate entities and also are reassembled
into their original coordinates in the 'summary' image. Parts of the
reconstructed image not included in the subframes are given a value
of zero.
Darks are acquired in a different mode than normal images, leading to
different cropping and therefore different image file structure.
Darks are acquired as full 1092x1056 pixel images, which are cropped
due to operational considerations to include 1088x1056 (Frame 0) and
4x1056 (Frame 6) allowing the complete reconstruction of the original
full frame. In contrast, normal images are cropped into several
smaller sections (the most prominent of which is the 1024x1024 active
area), and therefore have several smaller frames.
For further details on the layout of the data and the possible
combinations of frames, please refer to the Software Interface
Specification.
The label contains all relevant housekeeping information in calibrated
form (e.g. degrees Celsius, volts, or amperes).
Summary of Observations
=======================
The following table contains a listing of FC2 observations at Ceres.
Note that the abbreviation Sat. is used for Satellite in the table
below to keep the width within the allowable number of characters.
========================================================================
Dawn Ceres Prime Mission Science Observations
------------------------------------------------------------------------
Start Mission Activity Activity
Date Phase Name Description
========================================================================
14-12-26 CSA APPROACH Ceres Science Approach Phase
------------------------------------------------------------------------
15-01-13 CSA OPNAV_001 40 FC OpNav images
15-01-25 CSA OPNAV_002 40 FC OpNav images
15-02-04 CSA SAT_SEARCH_1 192 Sat. search images - Off-Ceres Pointing
15-02-04 CSA OPNAV_003 40 OpNav images + 180 Sat. search images
15-02-04 CSA SAT_SEARCH_2 256 Sat. search images - Off-Ceres Pointing
15-02-12 CSA RC1 171 FC rotational char #1 clear+color imgs
15-02-19 CSA RC2 232 FC rotational char #2 clear+color imgs
15-02-25 CSA OPNAV_004 40 OpNav images + 180 Sat. search images
15-03-01 CSA OPNAV_005 40 OpNav images + 103 Sat. search images
15-04-10 CSA OPNAV_006 40 OpNav images + 180 Sat. search images
15-04-15 CSA OPNAV_007 40 OpNav images + 180 Sat. search images
------------------------------------------------------------------------
15-04-24 CSR RC3 Ceres Science Rot Char 3 (range ~14030 km)
------------------------------------------------------------------------
15-04-25 CSR RC3 115 RC3 Eq. Limb 1 (South) high phase imgs
15-04-26 CSR RC3 54 HighPhaseSouth_001 clear images
15-04-26 CSR RC3 180 HighPhaseSouth_002 clear images
15-04-27 CSR RC3 363 HighPhaseSouth_003 clear images
15-04-29 CSR RC3 551 HighPhaseNorth_001 clear images
15-04-29 CSR RC3 270 HighPhaseNorth_002 clear images
15-04-30 CSR RC3 114 HighPhaseNorth_003 clear images
15-04-30 CSR RC3 42 RC3 Eq. Limb 2 (North) high phase imgs
15-05-01 CSR RC3 120 RC3 Eq. Limb 3 (North) high phase imgs
15-05-04 CSR RC3 249 RC3 North lit side clear+color images
15-05-05 CSR RC3 249 RC3 Equator lit side clear+color images
15-05-07 CSR RC3 249 RC3 South lit side clear+color images
------------------------------------------------------------------------
15-05-09 CTS TRANSFER_ Ceres Transfer to Survey Phase
TO_Survey
------------------------------------------------------------------------
15-05-16 CTS OPNAV_008 40 FC OpNav images
15-05-22 CTS OPNAV_009 40 FC OpNav images
------------------------------------------------------------------------
15-06-04 CSS SURVEY Ceres Science Survey Phase (range ~4870 km)
------------------------------------------------------------------------
15-06-05 CSS CYCLE1 191 nadir clear + color + 71 limb clear
15-06-08 CSS CYCLE2 193 nadir clear + color + 45 limb clear
15-06-11 CSS CYCLE3 212 nadir clear + color images
15-06-14 CSS CYCLE4 190 nadir clear + color + 73 limb clear
15-06-17 CSS CYCLE5 207 nadir clear + color images
15-06-21 CSS CYCLE6 210 nadir clear + color images
15-06-24 CSS CYCLE7 230 nadir clear + color images
15-06-27 CSS CYCLE8 Data lost to instrument reset
------------------------------------------------------------------------
15-07-01 CTH TRANSFER_ Ceres Transfer to HAMO Phase
TO_HAMO
------------------------------------------------------------------------
No science observations in this phase
------------------------------------------------------------------------
15-08-17 CSH HAMO Ceres Science HAMO Phase (range ~1950 km)
------------------------------------------------------------------------
15-08-18 CSH CYCLE1 2640 nadir clear+color images (12 orbits)
15-08-29 CSH CYCLE2 431 off-nadir clear images (12 orbits)
15-09-09 CSH CYCLE3 204 off-nadir clear images (12 orbits)
15-09-20 CSH CYCLE4 598 off-nadir clear images (12 orbits)
15-10-01 CSH CYCLE5 2422 nadir clear+color images (12 orbits)
15-10-12 CSH CYCLE6 408 off-nadir clear images (12 orbits)
------------------------------------------------------------------------
15-10-23 CTL TRANSFER_ Ceres Transfer to LAMO Phase
TO_LAMO
------------------------------------------------------------------------
No science observations in this phase
------------------------------------------------------------------------
15-12-16 CSL LAMO Ceres Science LAMO Phase (range ~850 km)
------------------------------------------------------------------------
15-12-16 CSL CYCLE0 436 nadir clear (1 seg)
15-12-18 CSL CYCLE1 3957 nadir clear (5 segs)
16-01-10 CSL CYCLE2 3795 nadir clear (5 segs)
16-02-02 CSL CYCLE3 3579 nadir clear (5 segs)
16-02-25 CSL CYCLE4 1638 nadir clear (5 segs)
16-03-19 CSL CYCLE5 1364* nadir clear+color(5 segs)
16-04-11 CSL CYCLE6 2778 nadir clear (5 segs)
16-05-04 CSL CYCLE7 2716 nadir clear (5 segs)
16-05-27 CSL CYCLE8 4065 nadir clear+color (5 segs)
========================================================================
Dawn Ceres Extended Mission 1 Science Observations
------------------------------------------------------------------------
16-06-19 CXL XMO1** Ceres Extended LAMO Phase (range ~850 km)
------------------------------------------------------------------------
16-06-19 CXL CYCLE9 4486 nadir clear+color (5 segs)
16-07-16 CXL CYCLE10 5142 nadir clear+color (6 segs)
16-08-10 CXL CYCLE11 4189 nadir clear+color (5 segs, seg 5 lost)
------------------------------------------------------------------------
16-09-02 CTJ TRANSFER_ Ceres Transfer to Juling Phase
TO_JULING
------------------------------------------------------------------------
No FC science observations in this phase
------------------------------------------------------------------------
16-10-10 CXJ XMO2 Ceres Extended Juling Phase (range ~1950 km)
------------------------------------------------------------------------
16-10-10 CXJ CYCLE1 1879 nadir clear+color (9 orbits)
16-10-24 CXJ CYCLE2 1050 nadir clear+color (7 orbits)
------------------------------------------------------------------------
16-11-03 CTG TRANSFER_ Ceres Transfer to GRaND Phase
TO_GRAND
------------------------------------------------------------------------
No FC science observations in this phase
------------------------------------------------------------------------
16-12-14 CXG XMO3 Ceres Extended GRaND Phase (range ~8000-9500 km)
------------------------------------------------------------------------
16-12-14 CXG CYCLE1 no images acquired (6 orbits)
17-01-21 CXG CYCLE2 989 FC2 nadir clear+color (3 orbits)
17-02-17 CXG CYCLE3 307 FC2~nadir clear+color (1 orbit)
107 FC1~nadir clear+color
------------------------------------------------------------------------
17-02-23 CTO TRANSFER_ Ceres Transfer to Opposition Phase
TO_OPPOSITION
------------------------------------------------------------------------
17-03-28 OpNav1 43 Ceres/Star exposure images
17-04-15 OpNav2 43 Ceres/Star exposure images
17-04-17 OpNav3 43 Ceres/Star exposure images
------------------------------------------------------------------------
17-04-28 CXO XMO4 Ceres Extended Opposition Phase (range 14-55E3 km)
------------------------------------------------------------------------
17-04-29 CX0 Opposition 205 FC2~nadir clear+color (range ~20,000 km)
199 FC1~nadir clear+color
17-05-17 OpNav4 43 Ceres/Star exposure images
========================================================================
Dawn Ceres Extended Mission 2 Science Observations
------------------------------------------------------------------------
17-07-01 CX2 XMO5 Ceres Extended Mission 2 Phase (range ~15000 km)
------------------------------------------------------------------------
18-01-09 Checkout 65 non-pointed clear and color
------------------------------------------------------------------------
18-04-15 CTI TRANSFER_ Ceres Transfer to Intermediate Orbit
TO_INTERMEDIATE
------------------------------------------------------------------------
No FC science observations in this phase
------------------------------------------------------------------------
18-05-15 C2I XMO6 Ceres Extended 2 Intermediate (range ~1950 km)
------------------------------------------------------------------------
18-05-15 C2I XMO6 1333 nadir clear+color (10 orbits)
------------------------------------------------------------------------
18-05-31 CTE TRANSFER_ Ceres Transfer to Elliptical Phase
TO_ELLIPTICAL
------------------------------------------------------------------------
No FC science observations in this phase
------------------------------------------------------------------------
18-06-09 C2E XMO7 Ceres Extended 2 Elliptical (peri range ~35 km)
------------------------------------------------------------------------
18-06-09 C2E da942 899 nadir clear only (5 orbits)
18-06-15 C2E da942 903 nadir clear only (5 orbits)
18-06-21 C2E da942 550 nadir Cerelia at Periapsis (3 orbits)
18-06-25 C2E da942 960 nadir clear only (5 orbits)
18-07-02 C2E da942 983 nadir clear only (5 orbits)
18-07-08 C2E da943 799 nadir clear only (5 orbits)
18-07-15 C2E da943 1006 nadir clear only (5 orbits)
18-07-22 C2E da943 708 nadir clear only (5 orbits)
18-07-29 C2E da943 879 nadir clear and color (5 orbits)
18-08-05 C2E da944 595 nadir clear only (5 orbits)
18-08-11 C2E da944 813 nadir and limb clear only (5 orbits)
18-08-18 C2E*** da944 416 nadir clear only (5 orbits)
18-08-25 C2E da944 530 nadir clear and color (5 orbits)
18-09-01 C2E da945 149 ~nadir clear only (1 orbit)
18-09-29 C2E da946 136 star calibration (1 orbit)
------------------------------------------------------------------------
* Data volume in LAMO Cycle 5 was perferentially assigned to the VIR
instrument. Clear images were taken in selected orbits with lossless
compression so that compression artifacts in other nadir cycles could
be assessed by comparison.
** Instrument resets and other issues resulted in the loss of many
images in XMO1, and some raw images that are included in the archive
could not be routinely processed. Since the project did not know if
it would be staying at Ceres or departing for Adeona, expensive orbit
maintenance maneuvers were not performed. As a result, the s/c was
far off the predicted trajectory. Many images were acquired on the
dark side of Ceres and color images missed their intended targets.
*** Missing 104 images from orbit 65 on Aug 21(233) to unknown ground
system (GDS) error.
Comment on Extended Mission 2 (XM2)Observations
===============================================
The XM2 orbits were highly elliptical and the argument of periapses
evolved rapidly during orbits. In particular, the periapsis latitude
drifted to the south by a few tenths of a degree/orbit in XMO6 and
by 1.7 degree/orbit in XMO7. Eventually periapsis crossed the south
pole and on to the dark side of Ceres in late August. As a result,
there is a gradual decrease in the number of images acquired in each
XMO7 partition. Another peculiarity of XMO7 is that the orbit was
designed to be 3:1 resonant with the Ceres rotation period such that
the observed longitude band would cover the Occator crater. Small
forces acting on the spacecraft created a slight east-west oscillation
of the ground track, with a general eastward drift, that allowed a
swath of longitudes near Occator to be observed. In addition, this
swath covers the Urvara crater in the south so it was imaged in detail
as well. There are no images acquired in XMO7 orbit 11 as this time
period was used to do a trajectory correction manuever (TCM) that
targeted Cerealia Facula at periapsis in orbit 13. Orbits 12 and 14
also cover this region extending the high resolution coverage. Images
from these three orbits are included in their own subdirectory for
the users.
Coordinate System
=================
The geometry items SC_SUN_POSITION_VECTOR,
SC_TARGET_POSITION_VECTOR and SC_TARGET_VELOCITY_VECTOR
provided in the label of the data product are relative to the
Earth Mean Equator frame of J2000.
SUB_SPACECRAFT_LATITUDE, SUB_SPACECRAFT_LONGITUDE are
given in the IAU PLANETOCENTRIC coordinate system. These parameters
are corrected for planetary and stellar aberrations.
Distances are given in km, angles in degrees.
|
| DATA_SET_RELEASE_DATE |
2015-09-04T00:00:00.000Z
|
| START_TIME |
2015-01-13T12:00:00.000Z
|
| STOP_TIME |
2018-09-29T12:00:00.000Z
|
| MISSION_NAME |
DAWN MISSION TO VESTA AND CERES
|
| MISSION_START_DATE |
2007-09-27T12:00:00.000Z
|
| MISSION_STOP_DATE |
2018-10-31T12:00:00.000Z
|
| TARGET_NAME |
1 CERES
|
| TARGET_TYPE |
ASTEROID
|
| INSTRUMENT_HOST_ID |
DAWN
|
| INSTRUMENT_NAME |
FRAMING CAMERA 2
|
| INSTRUMENT_ID |
FC2
|
| INSTRUMENT_TYPE |
FRAME CCD REFRACTING TELESCOPE
|
| NODE_NAME |
Small Bodies
|
| ARCHIVE_STATUS |
|
| CONFIDENCE_LEVEL_NOTE |
Image Processing
================
Through the analysis of Ceres Approach images it was determined that
there was a mean offset of 2.05 FC pixels in the FC2 boresight between
Vesta and Ceres. The reason for or source of this change in pointing
is unknown.
Exposure times
==============
Due to an idiosyncrasy of the proximity electronics, that takes
approximately 193 milliseconds from the commanding of the image
acquisition to the actual start of the exposure, the images report the
commanding time and the end of exposure. This results in a difference of
193 milliseconds between the usual calculation of exposure time
(STOP_TIME - START_TIME) and the reported EXPOSURE_DURATION, which is
always shorter than the difference of the other two.
Data Coverage
=============
There were very few major losses of FC2 data as of the end of
the Ceres HAMO mission phase. A DSN station problem resulted in the
loss of 77 images from the OpNav5 satellite search observation and an
unexpected transition between 1-way and 2-way communication during
the R2 playback resulted in the loss of 11 images (5 color, 6 clear).
At the LAMO/XMO1 altitude, the spacecraft small forces were
unpredictable and the spacecraft was often far from the expected ground
track. XMO1 was the most highly impacted part of the mission, partly
because the project expected to leave LAMO at the end of Cycle 9 and so
no course correction maneuver was planned. By the time the Cycle 11 was
being planned, the spacecraft was no longer following the predicted
trajectory, introducing significant gaps in coverage. In addition,
starting in HAMO and continuing thereafter, FC2 began to reset
unexpectedly while imaging. Images acquired before the camera reset
were not lost, but those that were expected to be acquired after the
reset were frequently lost or corrupted.
Data Quality
============
The following table contains a list of known lost or corrupted images.
---------------------------------------------------------------------
Lost or Corrupted Images
---------------------------------------------------------------------
Phase/Obs Image # Notes
---------------------------------------------------------------------
Approach OpNav5 77 of 220 images lost to DSN outage
Survey Cycle 8 660 of 660 images lost to instrument reset
HAMO Cycle 2 1 of 432 images lost to DSN issues
HAMO Cycle 3 257 of 462 images lost to instrument reset
LAMO Cycle 0 6 of 442 images lost to DSN issues
LAMO Cycle 1 26 of 3983 images lost to instrument reset
LAMO Cycle 2 171 of 3976 images lost to instrument reset
LAMO Cycle 3 25 of 3604 images lost to DSN issues
LAMO Cycle 4 167 of 1804 images lost to instrument reset
LAMO Cycle 5 30 of 1394 images lost to DSN issues
LAMO Cycle 6 0 of 2778 images lost
LAMO Cycle 7 0 of 2716 images lost
LAMO Cycle 8 1 of 4066 images lost to DSN issues
XMO1 Cycle 9 121 of 4650 images lost to instrument reset
XMO1 Cycle 10 11 of 5153 images lost to instrument reset
XMO1 Cycle 11 1056 of 5234 images lost to instrument reset
XMO2 Cycle 1 0 of 1879 images lost
XMO2 Cycle 2 160 of 1337 images lost to instrument reset
XMO3 Cycle 1 0 of 969 images lost
XMO3 Cycle 2 0 of 307 images lost
XMO4 OpNav001-004 0 of 43 images/observation lost
XMO4 Opposition 0 of 205 images lost
XMO6 5 of 1338 images lost to DSN issues
XMO7 da942 18 of 4321 images lost to DSN issues
XMO7 da943 0 of 3403 images lost
XMO7 da944 105 of 2470 images lost to unknown GDS issue
XMO7 da945 0 of 160 images lost
XMO7 da946 0 of 147 star cal images lost
DSN issues associated with
1) Dawn ephemeris errors resulting in not being pointed directly
at the DSN (C1),
2) Ephemeris errors altering occultation timing (C0),
3) Mountains in the way at low elevation angles at Canberra (C2, C3),
4) Wind at Goldstone (C3).
Most of the color images in XMO1 missed their planned targets because
the spacecraft was not on the predicted trajectory. In addition, many
of the clear images are either dark or have exposure durations that
were set for phase angles very different than those observed.
During XMO1 Cycle 10, segment 3, FC2 reset with a warm reboot.
Although the FEE was restarted by the onboard sequence, the camera
flight software came up with compression turned off. This greatly
increased the size of each image as well as the raw telemetry format
and these images could not be processed using the normal processing
pipeline. Images in the internal processing queue (color filter) and
those acquired after the reset (mix of filters) may be partially
corrupted.
During XMO2 (Juling), FC2 reset just before the start of the final orbit
of segment 2. This reset resulted in the loss of 276 planned high angle
views of Occator and Juling in all filters.
|
| CITATION_DESCRIPTION |
Nathues, A., H. Sierks, P. Gutierrez-Marques, J. Ripken, I. Hall, I.
Buettner, M. Schaefer, U. Chistensen,
DAWN FC2 RAW (EDR) CERES IMAGES V1.0,
DAWN-A-FC2-2-EDR-CERES-IMAGES-V1.0, NASA Planetary Data System,
2015.
|
| ABSTRACT_TEXT |
Abstract
========
This data set includes the Experiment Data Record (EDR) version of all
available images acquired during the Ceres Prime Mission (Approach,
Transfer to Survey, Survey, HAMO, and LAMO),and extended missions 1
(XMO1, XMO2, XMO3, XMO4) and 2 (XMO6, XMO7). In addition to the imagery,
ancillary information is stored within the image headers. Calibration
files needed for further processing are archived as a separate data set.
|
| PRODUCER_FULL_NAME |
PABLO GUTIERREZ-MARQUES
|
| SEARCH/ACCESS DATA |
SBN PSI WEBSITE
|
|
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