| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains Raw data taken by New Horizons
Multispectral Visible Imaging Camera
instrument during the PLUTO mission phase.
MVIC is a visible and near-infrared imager. MVIC comprises seven
separate CCD two-dimensional arrays; all rows are 5024 pixels across
with twelve pixels at either end of each row optically inactive. The
single Pan Frame array is a panchromatic frame-transfer imager, 5024x128
pixels, that typically takes multiple frames in each observation. The
common Pan Frame data product is an image cube in three dimensions:
spatial; spatial; image frame, equivalent to time. Of the remaining six
arrays, 5024x32 pixels each, two are panchromatic (unfiltered), and the
remaining four are under filters and called the color arrays:
Near-InfraRed (NIR); methane (CH4); Red; Blue. All six are operated in
Time-Delay Integration (TDI) mode; the TDI arrays are in some ways
similar to line cameras. In TDI mode, the spacecraft and MVIC boresight
are scanned across the target at a rate that matches the charge transfer
clock rate across the rows of the CCDs. Ideally the rates are matched,
so as the charges are read by the analog-to-digital converter off the
last line of the array, each pixel reading is near-proportional to the
brightness of the same piece of the target as its image moved across the
array, accumulating charge on each row. In TDI mode it is the product of
the per-row charge clock rate and the duration of the observation that
determines the number of rows each the image, and the image can be
arbitrarily long; the number of rows (32) in each array is not relevant
in determining the size of the image. The common data product for each
of the TDI arrays is a 2-D image, of arbitrary length as noted earlier.
During the Pluto mission phase starting in January, 2015, there were
several sub-phases: three Approach sub-phases, (AP1, AP2 and AP3); a
CORE sequence for the Pluto flyby on 14.July, 2015 (Day Of Year 195),
sometimes also referred to as NEP (Near-Encounter Phase); three
Departure sub-phases (DP1, DP2, DP3). For this first Ralph-MVIC
delivery for the Pluto mission phase, this data set includes only the
Approach data plus the subset of the CORE sequence data that was
downlinked through the end of July, 2015. The rest of the Pluto data
will be delivered in future versions of this data set according to the
schedule worked out by the Project and NASA.
On Approach during April, May and June of 2015, MVIC operations
included the following: functional tests; full color observations of
the Pluto, Charon and the other Plutonian satellites; Critical and
Non-critical Optical Navication (OpNav or NAV) observations. The color
observations were grouped over several 6-day periods to obtain a full
rotation of Pluto and Charon.
This dataset includes the first PC_VISUV_MAP for MVIC at about 19 days
before encounter, a color TDI observation looking for changes in color
and composition over multiple rotations, to meet the goal of
understanding the time variability of Pluto's surface. These
observations were repeated daily over that week leading up to
encounter. From the day of encounter, this data set includes data from
three CORE observations: (1) Pluto/Charon color map (PC_MULTI_MAP)
about a day before the Time of Closest Approach (P-1d); (2) Pluto and
Charon color scan at P-5h (PC_COLOR_1); (3) Nix color scan (N_COLOR_2).
The PC_MULTI_MAP observation, the last one of which is included in this
dataset, met multiple goals including imaging for color and surface
composition maps of the Pluto and Charon hemispheres, Pluto and Charon
phase integrals with resolved whole-disk images near 15 degrees, and
imaging Pluto hazes on approach. Secondary goals are Pluto and Charon
color high and low phase imaging to enable integrating over wavelength
to determine the bolometric Bond albedo, and also to investigate the
surface microphysics of Pluto and Charon, studying compositional and
textural stratification in the surface as a function of terrain type.
The N_COLOR series provided Nix high-resolution resolved color images.
Every observation provided in this data set was taken as a part of a
particular sequence. A list of these sequences has been provided in
file DOCUMENT/SEQ_MVIC_PLUTO.TAB.
N.B. Some sequences provided may have no corresponding observations.
For a list of observations, refer to the data set index table. This
is typically INDEX.TAB initially in the INDEX/ area of the data set.
There is also a file SLIMINDX.TAB in INDEX/ that summarizes key
information relevant to each observation, including which sequence
was in effect and what target was likely intended for the
observation.
Version
=======
This is VERSION 1.0 of this data set.
Processing
==========
The data in this data set were created by a software data
processing pipeline on the Science Operation Center (SOC) at
the Southwest Research Institute (SwRI), Department of Space Studies.
This SOC pipeline assembled data as FITS files from raw telemetry
packets sent down by the spacecraft and populated the data labels
with housekeeping and engineering values, and computed geometry
parameters using SPICE kernels. The pipeline did not resample
the data.
Data
====
The observations in this data set are stored in data files using
standard Flexible Image Transport System (FITS) format. Each FITS
file has a corresponding detached PDS label file, named according
to a common convention. The FITS files may have image and/or table
extensions. See the PDS label plus the DOCUMENT files for a
description of these extensions and their contents.
This Data section comprises the following sub-topics:
- Filename/Product IDs
- Instrument description
- Other sources of information useful in interpreting these Data
- Visit Description, Visit Number, and Target in the Data Labels
Filename/Product IDs
--------------------
The filenames and product IDs of observations adhere to a
common convention e.g.
MC0_0123456789_0X530_ENG.FIT
^^^ ^^^^^^^^^^ ^^^^^ ^^^\__/
| | | | ^^
| | | | |
| | | | +--File type (includes dot)
| | | | - .FIT for FITS file
| | | | - .LBL for PDS label
| | | | - not part of product ID
| | | |
| | | +--ENG for CODMAC Level 2 data
| | | SCI for CODMAC Level 3 data
| | |
| | +--Application ID (ApID) of the telemetry data
| | packet from which the data come
| |
| +--MET (Mission Event Time) i.e. Spacecraft Clock
|
+--Instrument designator
Note that, depending on the observation, the MET in the data filename
and in the Product ID may be similar to the Mission Event Time (MET)
of the actual observation acquisition, but should not be used as an
analog for the acquisition time. The MET is the time that the data are
transferred from the instrument to spacecraft memory and is therefore
not a reliable indicator of the actual observation time. The PDS label
and the index tables are better sources to use for the actual timing of
any observation. The specific keywords and index table column names for
which to look are
* START_TIME
* STOP_TIME
* SPACECRAFT_CLOCK_START_COUNT
* SPACECRAFT_CLOCK_STOP_COUNT
Instrument Instrument designators ApIDs
=========== ================================== =============
MVIC MC0, MC1, MC2, MC3, MP1, MP2, MPF 0X530 - 0X54A *
* Not all values in this range are in this data set
There are other ApIDs that contain housekeeping values and
other values. See SOC Instrument ICD (/DOCUMENT/SOC_INST_ICD.*)
for more details.
Here is a summary of the meanings of each instrument designator:
Instr
Dsgn. Description
===== ===========
MC0 MVIC, Color TDI, Red filter
MC1 MVIC, Color TDI, Blue filter
MC2 MVIC, Color TDI, Near-InfraRed (NIR) filter
MC3 MVIC, Color TDI, Methane (CH4) filter
MP1 MVIC, Panchromatic TDI CCD 1
MP2 MVIC, Panchromatic TDI CCD 2
MPF MVIC, Panchromatic frame (5024 pixels)
See SOC Instrument ICD (/DOCUMENT/SOC_INST_ICD.*) for details
Here is a summary of the types of files generated by each ApID
along with the instrument designator that go with each ApID:
ApIDs Data product description/Prefix(es)
===== ===================================
0x530 - MVIC Panchromatic TDI Lossless (CDH 1)/MP1,MP2
0x53f - MVIC Panchromatic TDI Lossless (CDH 2)/MP1,MP2
0x531 - MVIC Panchromatic TDI Packetized (CDH 1)/MP1,MP2
0x540 - MVIC Panchromatic TDI Packetized (CDH 2)/MP1,MP2
0x532 - MVIC Panchromatic TDI Lossy (CDH 1)/MP1,MP2
0x541 - MVIC Panchromatic TDI Lossy (CDH 2)/MP1,MP2
0x533 - MVIC Panchromatic TDI 3x3 Binned Lossless (CDH 1)/MP1,MP2 *
0x542 - MVIC Panchromatic TDI 3x3 Binned Lossless (CDH 2)/MP1,MP2 *
0x534 - MVIC Panchromatic TDI 3x3 Binned Packetized (CDH 1)/MP1,MP2 *
0x543 - MVIC Panchromatic TDI 3x3 Binned Packetized (CDH 2)/MP1,MP2 *
0x535 - MVIC Panchromatic TDI 3x3 Binned Lossy (CDH 1)/MP1,MP2 *
0x544 - MVIC Panchromatic TDI 3x3 Binned Lossy (CDH 2)/MP1,MP2 *
0x536 - MVIC Color TDI Lossless (CDH 1)/MC0,MC1,MC2,MC3
0x545 - MVIC Color TDI Lossless (CDH 2)/MC0,MC1,MC2,MC3
0x537 - MVIC Color TDI Packetized (CDH 1)/MC0,MC1,MC2,MC3
0x546 - MVIC Color TDI Packetized (CDH 2)/MC0,MC1,MC2,MC3
0x538 - MVIC Color TDI Lossy (CDH 1)/MC0,MC1,MC2,MC3
0x547 - MVIC Color TDI Lossy (CDH 2)/MC0,MC1,MC2,MC3
0x539 - MVIC Panchromatic Frame Transfer Lossless (CDH 1)/MPF
0x548 - MVIC Panchromatic Frame Transfer Lossless (CDH 2)/MPF
0x53a - MVIC Panchromatic Frame Transfer Packetized (CDH 1)/MPF
0x549 - MVIC Panchromatic Frame Transfer Packetized (CDH 2)/MPF
0x53b - MVIC Panchromatic Frame Transfer Lossy (CDH 1)/MPF
0x54a - MVIC Panchromatic Frame Transfer Lossy (CDH 2)/MPF
* as of October, 2014, 3x3 modes have not been used
Instrument description
----------------------
Refer to the following files for a description of this instrument.
CATALOG
MVIC.CAT
DOCUMENTS
RALPH_SSR.*
SOC_INST_ICD.*
NH_RALPH_V###_TI.TXT (### is a version number)
Other sources of information useful in interpreting these Data
--------------------------------------------------------------
Refer to the following files for more information about these data
NH Trajectory tables:
/DOCUMENT/NH_MISSION_TRAJECTORY.* - Heliocentric
RALPH Field Of View definitions:
/DOCUMENT/NH_FOV.*
/DOCUMENT/NH_RALPH_V###_TI.TXT
Visit Description, Visit Number, and Target in the Data Labels
---------------------------------------------------------------
The observation sequences were defined in Science Activity Planning
(SAP) documents, and grouped by Visit Description and Visit Number.
The SAPs are spreadsheets with one Visit Description & Number per row.
A nominal target is also included on each row and included in the data
labels, but does not always match with the TARGET_NAME field's value in
the data labels. In some cases, the target was designated as RA,DEC
pointing values in the form ``RADEC=123.45,-12.34'' indicating Right
Ascension and Declination, in degrees, of the target from the
spacecraft in the Earth Equatorial J2000 inertial reference frame.
This indicates either that the target was either a star, or that the
target's ephemeris was not loaded into the spacecraft's attitude and
control system which in turn meant the spacecraft could not be pointed
at the target by a body identifier and an inertial pointing value had
to be specified as Right Ascension and Declination values. The PDS
standards do not allow putting a value like RADEC=... in the PDS
TARGET_NAME keyword's value. In those cases the PDS TARGET_NAME value
is set to CALIBRATION.
Ancillary Data
==============
The geometry items included in the data labels were computed
using the SPICE kernels archived in the New Horizons SPICE
data set, NH-X-SPICE-6-PLUTO-V1.0.
Every observation provided in this data set was taken as a part of a
particular sequence. A list of these sequences has been provided in
file DOCUMENT/SEQ_MVIC_PLUTO.TAB. In addition, the
sequence identifier (ID) and description are included in the PDS label
for every observation. N.B. While every observation has an associated
sequence, every sequence may not have associated observations; that is,
some sequences may have failed to execute due to spacecraft events
(e.g. safing) and there will be observations associated with those
sequences. No attempt has been made during the preparation of this
data set to identify if any, or how many, such empty sequences there
are, so it is up to the user to compare the times of the sequences
to the times of the available observations from the INDEX/INDEX.TAB
table to identify such sequences.
Time
====
There are several time systems, or units, in use in this dataset:
New Horizons spacecraft MET (Mission Event Time or Mission Elapsed
Time), UTC (Coordinated Universal Time), and TDB Barycentric
Dynamical Time.
This section will give a summary description of the relationship
between these time systems. For a complete explanation of these
time systems the reader is referred to the documentation
distributed with the Navigation and Ancillary Information
Facility (NAIF) SPICE toolkit from the PDS NAIF node, (see
http://naif.jpl.nasa.gov/).
The most common time unit associated with the data is the spacecraft
MET. MET is a 32-bit counter on the New Horizons spacecraft that
runs at a rate of about one increment per second starting from a
value of zero at
19.January, 2006 18:08:02 UTC
or
JD2453755.256337 TDB.
The leapsecond adjustment (DELTA_ET = ET - UTC) over this dataset
is 65.184s.
The data labels for any given product in this dataset usually
contain at least one pair of common UTC and MET representations
of the time at the middle of the observation. Other portions
of the products, for example tables of data taken over periods
of up to a day or more, will only have the MET time associated
with a given row of the table.
For the data user's use in interpreting these times, a reasonable
approximation (+/- 1s) of the conversion between Julian Day (TDB)
and MET is as follows:
JD TDB = 2453755.256337 + ( MET / 86399.9998693 )
For more accurate calculations the reader is referred to the
NAIF/SPICE documentation as mentioned above.
Reference Frame
===============
Geometric Parameter Reference Frame
-----------------------------------
Earth Mean Equator and Vernal Equinox of J2000 (EMEJ2000) is the
inertial reference frame used to specify observational geometry items
provided in the data labels. Geometric parameters are based on best
available SPICE data at time of data creation.
Epoch of Geometric Parameters
-----------------------------
All geometric parameters provided in the data labels were computed at
the epoch midway between the START_TIME and STOP_TIME label fields.
Software
========
The observations in this data set are in standard FITS format
with PDS labels, and can be viewed by a number of PDS-provided
and commercial programs. For this reason no special software is
provided with this data set.
Contact Information
===================
For any questions regarding the data format of the archive,
contact
New Horizons RALPH Principal Investigator:
Alan Stern, Southwest Research Institute
S. Alan Stern
Southwest Research Institute
Department of Space Studies
1050 Walnut Street, Suite 400
Boulder, CO 80302
USA
|
| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
During the processing of the data in preparation for
delivery with this volume, the packet data associated with each
observation were used only if they passed a rigorous verification
process including standard checksums.
In addition, raw (Level 2) observation data for which adequate
contemporary housekeeping and other ancillary data are not available
may not be reduced to calibrated (Level 3) data. This issue is raised
here to explain why some data products in the raw data set,
NH-P-MVIC-2-PLUTO-V1.0,
may not have corresponding data products in the calibrated data set,
NH-P-MVIC-3-PLUTO-V1.0.
Data coverage and quality
=========================
Caveat about TARGET_NAME in PDS labels and observational intent
===============================================================
A fundamental truth of managing data from some spacecraft missions
is that the intent of any observation is not suitable for insertion
into the command stream sent to the spacecraft to execute that
observation. As a result, re-attaching that intent to the data
that are later downlinked is problematic at best. For New Horizons
that task is made even more difficult as the only meta-data that
come down with the observation is the unpredictable time of the
observation. The task is made yet even more difficult because
uplink personnel, who generate the command sequences and initially
know the intent of each observation, are perpetually under
deadlines imposed by orbital mechanics and can rarely be spared for
the time-intensive task of resolving this issue.
To make a long story short, the downlink team on New Horizons has
created an automated system to take various uplink products, decode
things like Chebyshev polynomials in command sequences representing
celestial body ephemerides for use on the spacecraft to control
pointing, and infer from those data what the most likely intended
target was at any time during the mission. This works well during
flyby encounters and less so during cruise phases and hibernation.
The point to be made is that the user of these PDS data needs to
be cautious when using the TARGET_NAME and other target-related
parameters stored in this data set. This is less an issue for the
plasma and particle instruments, more so for pointing instruments.
To this end, the heliocentric ephemeris of the spacecraft, the
spacecraft-relative ephemeris of the inferred target, and the
inertial attitude of the instrument reference frame are provided
with all data, in the J2000 inertial reference frame, so the user
can check where that target is in the Field Of View (FOV) of the
instrument. Furthermore, for pointing instruments with one or more
spatial components to their detectors, a table has been provided
in the DOCUMENT/ area with XY (two-dimensional) positions of each
inferred target in the primary data products. If those values are
several thousand pixels off of a detector array, it is a strong
indication that the actual target of that observation is something
other than the inferred target, or no target at all e.g. dark sky.
Review
======
This dataset was peer reviewed and certified for scientific use on
TBD.
|
.png)
.png)
