Data Set Information
|
| DATA_SET_NAME |
NEW HORIZONS
REX PLUTO ENCOUNTER
CALIBRATED V1.0
|
| DATA_SET_ID |
NH-P-REX-3-PLUTO-V1.0
|
| NSSDC_DATA_SET_ID |
|
| DATA_SET_TERSE_DESCRIPTION |
Calibrated data taken by New Horizons
Radio Science Experiment
instrument during the PLUTO mission phase.
This is VERSION 1.0 of this data set.
|
| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains Calibrated data taken by New Horizons
Radio Science Experiment
instrument during the PLUTO mission phase.
The REX instrument measures the amplitude and phase of radio signals
captured by the New Horizons high-gain antenna. The main investigation
is an occultation experiment which uses radio signals transmitted from
Earth to probe the atmosphere and ionosphere of Pluto and Charon.
Ancillary investigations include measurements of the 4 cm wavelength
radiothermal emission from planets or other radio sources. Phase data
may also be combined with Pluto encounter tracking data, derived from
the Radio Science Subsystem separately from REX and to be archived in
separate non-REX data set(s), to infer the influence of gravitational
fields on the spacecraft as it moves through the Pluto system.
The main investigation requires coordinated use of the Earth-based
transmitters and the spacecraft receiver as the two physical elements
of the REX instrument. The 'Ground Element' comprises DSN (Deep Space
Network) hardware and operations facilities on Earth, and the 'Flight
Element' includes signal processing hardware and software onboard the
spacecraft.
Unless inclusion of tuning profiles for one-way uplink transmissions is
noted below, this data set includes only samples taken and measurements
made by the REX system hardware on-board the New Horizons spacecraft --
either of one-way uplink signals or of 4cm-wavelength thermal emission.
#######################################################################
#######################################################################
REQUIRED UNDERSTANDING: THE REX AND THE NEW HORIZONS (NH) REGENERATIVE
RANGING TRACKER [DEBOLTETAL2005] ARE
*****SEPARATE***** AND *****INDEPENDENT*****
SUBSYSTEMS THAT BOTH USE THE RADIO FREQUENCY (RF) AND TELECOMMUNICATION
SUBSYSTEMS. TRACKING DATA WILL NOT BE ARCHIVED IN REX DATA SETS.
#######################################################################
#######################################################################
During the Pluto Charon Encounter 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); a Transition
sub-phase which ran to the end of the mission phase. For this final
REX delivery for the Pluto mission phase, this data set includes all
data that were downlinked through the end of the Pluto Encounter
mission phase in late October, 2016.
On Approach during April, May and June of 2015, REX executed only
tests and calibration sequences: test patterns; an Operational
Readiness Test (ORT) on 08.April of the surface temperature doublescan
(THERMSCAN) and of the Pluto and Charon occulations; ride-alongs with
several PEPSSI plasma rolls, which were performed with Deep Space
Network (DSN) uplink tones for USO characterization; a high-power
uplink test with the 34m antenna DSS-26. The timings of the plasma
roll USO characterizations were planned so that the Z axis was
oriented toward the Sun during rolls about the Y axis (HGA boresight)
pointed to Earth: this 'Z to Sun' attitude duplicated the orientation
that would occur during the Pluto and Charon occultations in the CORE
sequence.
From the day of encounter, this data set includes data from two CORE
observations: (1) the bi-static radar THERMSCAN data, which measured
DSN uplink signal reflected off of Pluto during the flyby; (2) the
Pluto occultation data for both ingress and egress.
There is also a backup USO Stability characterization observation
taken in November, 2015, to replace a attempt in the weeks after
encounter that failed due to a DSN misconfiguration.
In July, 2016, during the Transition sub-phase, two calibration
campaigns ran test patterns, USO characterization, HGA side lobe
characterization, and radiometer calibration (cold sky and radio
source).
This data set also includes uplink tuning profile data in, and
extracted from, Tracking and Navigation Files (TNFs) for all CORE
observations. Although uplink data signals were sent from the Ground
Element to REX during the Approach sub-phase, tuning profiles for
those signals are not provided as they are not needed to analyze those
REX Approach observations comprising instrument checkout,
characterization and calibration activities.
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_REX_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.
Known issues in REX data
========================
The following item assumes familiarity with the REX, REX terminology
and the required reading and other documentation provided with this
data set.
Time tag anomalies in ROF sequences
-----------------------------------
REX places ten incrementing time tags in each REX Output Frame (ROF).
The time tags can be used both to identify any breaks in a sequence of
ROFs, and to determine the time between any two ROFs within a
sequence.
The normal sequence for time tags is to start at zero in the first ROF
and increment ten times per ROF, so the first time tag of the second
ROF is 10, that of the third ROF is 20, etc. In practice, the first
and last ROFs in a sequence do not always show simple zero starts and
clean finishes, respectively, indicating data corruption in just those
ROFs. There is no indication of corruption elsewhere in ROF streams,
and REX commanding ensures there are always adequate ROFs before and
after any observation, so discarding starting and ending ROFs in a
sequence based on simple inspection of time tags is the way to handle
this issue.
For more detail, refer to the REX Instrument Description section in
the SOC Instrument Interface Control Document (ICD).
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 Operations Center (SOC) at
the Southwest Research Institute (SwRI), Department of Space Operations.
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.
Calibration
===========
Detailed information about calibration of REX data is available
in the SOC Instrument Interface Control Document (ICD) and
in the NH_REX_RADIOMETER_CALIB_V4P7 calibration report in the
DOCUMENT section of this data set; refer to these documents for
REX calibration details.
Note also that for REX data the Calibrated dataset is one version
behind the Raw dataset, so for example the Calibrated dataset would
be at Version 1.0 while the Raw dataset would be at Version 2.0.
There was an initial delivery to the PDS of the Raw dataset before
the Calibrated dataset was completed.
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.
REX_0123456789_0X7B0_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
| | N.B. ApIDs are case-insensitive
| |
| +--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 **
=========== ================================== =============
REX REX 0X7B0 - 0X7B3 *
* Not all values in this range are in this data set
** ApIDs are case insensitive
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 types of files generated by each ApID
(N.B. ApIDs are case-insensitive) along with the instrument
designator that go with each ApID:
ApIDs Data product description/Prefix(es)
===== ===================================
0x7b0 - REX Lossless Compressed Data (CDH 1)/REX
0x7b1 - REX Packetized Data (CDH 1)/REX
0x7b2 - REX Lossless Compressed Data (CDH 2)/REX
0x7b3 - REX Packetized Data (CDH 2)/REX
Instrument description
----------------------
Refer to the following files for a description of this instrument.
CATALOG
REX.CAT
DOCUMENTS
REX_SSR.*
SOC_INST_ICD.*
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
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. PDS-SBN
practices 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. TARGET_NAME may be N/A (Not Available or Not
Applicable) for a few observations in this data set; typically that
means the observation is a functional test so N/A is an appropriate
entry for those targets, but the PDS user should also check the
NEWHORIZONS:OBSERVATION_DESC and NEWHORIZONS:SEQUENCE_ID keywords in
the PDS label, plus the provided sequence list (see Ancillary Data
below) to assess the possibility that there was an intended target.
These two keywords are especially useful for STAR targets as often
stars are used as part of instrument calibrations, and are
included as part of the sequencing description which is captured
in these keywords.
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_REX_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. Some
sequences may have failed to execute due to spacecraft events (e.g.
safing). No attempt has been made during the preparation of this data
set to identify such empty sequences, so it is up to the user to
compare the times of the sequences to the times of the available
observations from INDEX/INDEX.TAB 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) was 65.184s at
NH launch, and the first three additional leapseconds occurred
in at the ends of December, 2009, June, 2012 and June, 2015.
Refer to the NH SPICE data set, NH-J/P/SS-SPICE-6-V1.0, and the
SPICE toolkit documentation, for more details about leapseconds.
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 REX Principal Investigator:
Ivan Linscott, Stanford University
David Packard Building - Room 319
350 Serra Mall
Stanford, CA 94305-9515
USA
|
| DATA_SET_RELEASE_DATE |
2017-04-30T00:00:00.000Z
|
| START_TIME |
2015-04-08T06:16:33.775Z
|
| STOP_TIME |
2016-07-12T11:59:25.062Z
|
| MISSION_NAME |
NEW HORIZONS
|
| MISSION_START_DATE |
2006-01-19T12:00:00.000Z
|
| MISSION_STOP_DATE |
2016-10-26T12:00:00.000Z
|
| TARGET_NAME |
SKY
CALIBRATION
EARTH
CHARON
M 1
PLUTO
|
| TARGET_TYPE |
CALIBRATION
CALIBRATION
PLANET
SATELLITE
NEBULA
PLANET
|
| INSTRUMENT_HOST_ID |
NH
|
| INSTRUMENT_NAME |
RADIO SCIENCE EXPERIMENT
|
| INSTRUMENT_ID |
REX
|
| INSTRUMENT_TYPE |
RADIO SCIENCE
|
| NODE_NAME |
Small Bodies
|
| ARCHIVE_STATUS |
LOCALLY ARCHIVED
|
| 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
may not have corresponding data products in the calibrated data set.
Note that the REX Raw V2.0 dataset corresponds with the REX
Calibrated V1.0 dataset. The Raw data had been certified once before
the calibrated data was able to be certified.
Data coverage and quality
=========================
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_REX_PLUTO.TAB. N.B. Some sequences
provided may have zero corresponding observations.
Refer to the Confidence Level Overview section above for a summary
of steps taken to assure data quality.
The calibrated radiometry values in the data products of this data
set are supplied in units of dBm. The conversion to dBm includes the
logarithm of a raw power value. For cases where that raw power value
is zero, the logarithm function used returns the IEEE_REAL floating
point special value for negative infinity (-Inf). This is correct
behavior, and that IEEE_REAL special value for negative infinity is
stored in the data file. However, PDS3 has no way to recognize this
as negative infinity, and will instead interpret the bits in the data
as -340282366920938463463374607431768211456.0, or about -3.4E+38. To
deal with this, the radiometry COLUMN OBJECT will contain the
VALID_MINIMUM keyword with a value sufficiently small to flag the
IEEE-754 -Inf values as invalid, whether they are interpreted as the
special IEEE-754 value negative infinity or as the numeric -3.4E+38.
In practice, this only occurs in situations where the raw accumulated
power is being initialized, or where the raw power data are zeroed
because REX has been shut down before completion of a final REX
Output Frame (ROF; see the ICD), or where the instrument input is a
non-physical synthetic signal used to validate correct operation of
the REX instrument. In all of these cases, this behavior is easily
identified and will have no effect on any science analysis.
The Time Tag counter values included with REX data normally increment
nine times within each data file and once between consecutive frames.
However, there are sometimes anomalous departures from this behavior at
the start and end of contiguous runs of data files (see REX.CAT for a
brief discussion of such an issue related to compression). Files with
such anomalies are few compared to the total number of data files, and
excluding those files with anomalous Time Tag data from data analysis
will not significantly affect the results of the REX investigation.
Refer to the Science Operations Center/instrument interface control
document for more detail about REX Time Tags; there is adequate
information there for users to identify anomalous files.
In addition, products with Time Tag anomalies are listed in file
ERRATA.TXT provided with this data set.
Observation descriptions in this data set catalog
=================================================
Some users will expect to find descriptions of the observations
in this data set here, in this Confidence Level Note. This data
set follows the more common convention of placing those
descriptions under the Data Set Description (above, if the user is
reading this in the DATASET.CAT file) of this data set catalog.
Caveat about TARGET_NAME in PDS labels and observational intent
===============================================================
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 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.
Finally, note that, within the FITS headers of the data products,
the sequence tables, and other NH Project-internal documents used
in this data set and/or inserted into the data set catalog,
informal names are often used for targets instead of the canonical
names required for the TARGET_NAME keyword. For example, during
the Pluto mission phase, instead of the TARGET_NAME '15810 ARAWN
(1994 JR1)' there might be found any of the following: 1994JR1;
1994 JR1; JR1. For all values where the PDS keyword TARGET_NAME
is used (e.g. in PDS labels and in index tables), the canonical,
PDS-approved names are used (if not, please bring this to the
attention of PDS so it can be rectified). However, within the
context of this data set, these project abbreviations are not
ambiguous (e.g. there is only one NH target with 'JR1' in its
name), so there has been, and will be, no attempt to expand such
abbreviations where they occur outside formal PDS keyword values.
Review
======
This dataset was peer reviewed and certified for scientific use on
December 4, 2017.
|
| CITATION_DESCRIPTION |
Linscott, I., NEW HORIZONS
Calibrated REX PLUTO ENCOUNTER V1.0,
NH-P-REX-3-PLUTO-V1.0,
NASA Planetary Data System, 2018.
|
| ABSTRACT_TEXT |
This data set contains Calibrated data taken by the New Horizons
Radio Science Experiment
instrument during the
Pluto encounter
mission phase. This is VERSION 1.0 of this data set.
This data set contains REX observations taken during the
the Approach (Jan-Jul, 2015), Encounter, Departure, and
Transition mission sub-phases, including flyby observations
taken on 14 July, 2015, and departure and calibration data
through late October, 2016. This data set completes the
Pluto mission phase deliveries for REX.
The REX datasets over the mission include calibrations using known radio
sources, Jupiter, and cold sky measurements; operational readiness
tests (ORTs); internal test pattern calibration; and prime science
radiometry and occultation observations during the Pluto Encounter.
|
| PRODUCER_FULL_NAME |
TIFFANY FINLEY
|
| SEARCH/ACCESS DATA |
SBN Comet Website
|
|
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