Introduction
This User’s Guide provides a brief overview of the New Horizons Mission (NH or “nh:”) namespace for those working with data from New Horizons primary or extended missions. The primary New Horizons mission was to the Pluto system. The extended missions to date have been called the “Kuiper Belt Extended Missions 1 and 2”, or “KEM1” and “KEM2”, in the mission documentation and metadata.
Note that the New Horizons legacy data migration is in its early stages, with labels being designed for each instrument in turn. This namespace is in active development and will continue to be so for the forseeable future.
Data from the primary and first extended (“KEM1”) missions were archived in PDS3 format and migration is underway to convert the legacy data into PDS4. These migrated products will also serve as templates for the second extended (“KEM2”) mission, which will be delivered in PDS4 format.
This guide presents the major features of the namespace.
Overview of the New Horizons (NH) Mission Dictionary
The New Horizons Mission, the first to travel to the Pluto system, was launched in 2006 and flew past Pluto on 14 July 2015. After the successful completion of its primary mission, an extended mission was granted to investigate the Kuiper Belt Object (KOB) 2014 MU69 (Arrokoth). The New Horizons mission data were originally developed and archived in PDS3 format. This dictionary was developed as part of the PDS4 migration effort, and includes all phases of the primary and extended mission.
Primary Steward: Anne Raugh, Small Bodies Node, University of Maryland (@acraugh on Github)
Dictionary Repo: https://github.com/pds-data-dictionaries/ldd-nh
Namespace Prefix: nh:
Corrections, changes, and additions should be submitted through the PDS LDD Issue Repo.
Organization of Classes and Attributes
The New Horizons dictionary has a single top-level class that must be used to access any of the NH metadata classes. Below that, there are major subclasses for metadata that is common to all (or multiple instruments), as well as classes specific to particular instruments. Processed and calibrated data will generally have additional classes to provide instrument-specific processing details.
The following sections describe the major divisions of the New Horizons Mission namespace, in the order in which they occur in the schema (and thus, labels).
Top-Level Class: <nh:Mission_Parameters>
The <nh:Mission_Parameters> class acts as a wrapper for all other NH classes. It contains one required attribute and (as of this writing) two optional classes for data specific to the Multispectral Visible Imaging Camera (MVIC) part of in the Ralph instrument package.
The class contains a single required attribute, <nh:mission_phase_name>, with the string identifying the mission phase. Mission phase names are unique to the primary or extended mission in which they occur. Specifically, the phases in the extended missions contain the extended mission acronym (“KEM1 Encounter”, for example).
The major subclasses of the <nh:Mission_Parameters> class are:
You can see a complete outline of the namespace under the New Horizons Mission Namespace Outline topic.
Subclass: <nh:Observation_Parameters>
The <nh:Observation_Parameters> class provides details specific to the New Horizons mission and the instrument used to make the observation comprising the data product. It provides three attributes and two classes. As in the PDS common namespace, in the NH dictionary attributes names are all lowercase; class names are in title case.
This class contains:
<nh:telemetry_appid>
<nh:sequence_id>
<nh:observation_description>
<nh:Mission_Elapsed_Time>
<nh:Detector>
<nh:Spacecraft_State>
None of these components is repeatable; all are expected to be present in all raw and processed/calibrated data labels.
- <nh:telemetry_appid>, <nh:sequence_id>, and <nh:observation_description>
These attributes are provided primarily for provenance and to provide some minimal description of planned activities for the end user. The nh:telementry_appid is tied to instrument operating mode and to onboard processing like data compression. The mission documentation for each instrument will provide further detail if desired. The <nh:sequence_id> ties into the instrument observing plan, and the codes comprising that ID are roughly translated into something approaching English in the <nh:observation_description> string.
- <nh:Mission_Elapsed_Time>
The <nh:Mission_Elapsed_Time> class provides the spacecraft clock partition and count at the start and end of the observation comprising the data product. The translation from spacecraft clock to UTC is dependent on the hardware and is usually described in the mission documentation. Many missions and end-users use the publicly available Navigation and Ancillary Information (NAIF) Toolkit to perform this conversion.
- <nh:Detector>
The <nh:Detector> class identifies the detector used to make the observation, and includes classes to provide detector-specific parameters. “Detector” may mean an instrument, or it may mean literally one of several detectors available within an instrument (as is the case of the MVIC instrument, for example). This class will contain detector-specific subclasses where needed to provide specific observational settings for the detector.
- <nh:Spacecraft_State>
The <nh:Spacecraft_State> class provides information about thruster firings, spin state, scan rate, and spacecraft motion at the time of the observation. For cases where none of the attributes of this class are relevant to the data product, this class should be omitted.
Subclass: <nh:MVIC_Calibration_Information>
The <nh:MVIC_Calibration_Information> class is used in labels for processed data from all seven MVIC detectors. It provides detector-specific quantities used in processing the data, and in the case of the MVIC framing camers, it provides the specific left- and right-side biases used to process each frame.
This class contains:
<nh:physical_pixel_size>
<nh:read_noise>
<nh:gain>
<nh:tdi_median_bias_level>
<nh:Framing_Biases>
- <nh:physical_pixel_size>, <nh:read_noise> and <nh:gain>
The <nh:physical_pixel_size> value is constant for all pixels on all MVIC detectors. It is provided explicitly for the convenience of users further analyzing to the data. The <nh:read_noise> and <nh:gain> are also provided for all MVIC observations.
- <nh:tdi_median_bias_level>
The <nh:tdi_median_bias_level> appears only in processed time delay integration (TDI) observations, from the color channels and the two panchromatic TDI channels. Bias levels for the TDI channels are determined during cruise operations and may be updated through the course of the mission.
- <nh:Framing_Biases>
The <nh:Framing_Biases> class only appears in processing sequences from the MVIC framing array. It contains one <nh:Frame_Bias_Levels> class for each frame comprising the observation that identifies the frame by number and lists the left- and right-side bias levels applied in processing that particular frame. For framing observations, bias is measured during each observations using shielded pixels on either edge of the array.
Subclass: <nh:Radiometric_Conversion_Constants>
NOTE: As of version 1.1.0, this class replaces the deprecated <nh:MVIC_Conversion_Constants> class. The content of that class is included in this one, with additional constants added as needed. This class is used by multiple instruments.
The <nh:Radiometric_Conversion_Constants> class is used in labels for processed data from all seven MVIC detectors. The MVIC pipeline does not produce “calibrated” data in the sense that PDS defines “calibrated” - specifically, “Data reduced to physical units”. The final reduction step depends on both the spectal characteristics of the target and whether that target is resolved. Instead, the calibration documentation provided with the archive includes formulae for applying the absolute calibration for specific targets, and the constants needed to plug into the formulae are provided in this class.
This class contains:
<nh:pivot_wavelength>
<nh:Resolved_Source>
<nh:Unresolved_Source>
- <nh:pivot_wavelength>
The <nh:pivot_wavelength> attribute contains the pivot wavelength of the filter/dectector combination.
- <nh:Resolved_Source>
The <nh:Resolved_Source> class provides the units of measure (units of radiance, in the case of resolved targets) applicable to the resulting pixel values. Other attributes contain the conversion constants for five targets:
The Sun
Jupiter
(5145) Pholus, a centaur
Pluto
Charon
Arrokoth
- <nh:Unresolved_Source>
The <nh:Unresolved_Source> class provides the units of measure (units of irradiance, in the case of unresolved targets) applicable to the resulting pixel values. Other attributes contain the conversion constants for five targets:
The Sun
Jupiter
(5145) Pholus, a centaur
Pluto
Charon
Arrokoth
Subclass: <nh:REX_Radiometry_Information>
The <nh:REX_Radiometry_Information> class is used in labels for data from the Radio Science Experiment. The attributes in this class provide important instrument parameters and coefficients used to translate raw radiometer counts into physical units for a given product.
This class contains:
<nh:frame_data_source>
<nh:agc_gain_setting>
<nh:agc_setting_source>
<nh:agc_gain_provenance>
<nh:base_agc_gain>
<nh:base_power>
<nh:radio_bandwidth>
<nh:radiometry_response_step>
<nh:radiometry_response_offset>
<nh:iq_calibration_constant>
<nh:time_tag_calibration_constant>
- <nh:frame_data_source>
The <nh:frame_data_source> attribute indicates the source of the input as a two- digit hexadecimal number (i.e., one octet), represented as a string prefixed by ‘0x’. 0x00 is the default source when taking data of external 7.2 GHz signal or external radiometry. All other values indicate REX-internal sources intended for diagnostics. The 4 least significant bits and the single most significant bit are not used.
- <nh:agc_gain_setting>
The <nh:agc_gain_setting> attribute supplies the value of the AGC gain setting used in the radiometry calibration.
- <nh:agc_setting_source>
The <nh:agc_setting_source> attribute provides the source of the <nh:agc_gain_setting> value. This attribute will have a value of either ‘AUX’ or ‘ULCMD’.
- <nh:agc_gain_provenance>
The <nh:agc_gain_provenance> attribute supplies the provenance for the <nh:agc_gain_setting> attribute. If <nh:agc_setting_source> = ‘ULCMD’, this value will take the form ‘YYDOY.ssf:…’, where YY is the two-digit year, DOY is the day-of-year, and ‘…’ represents a string that indicates the source sequence file. Otherwise (if *<nh:agc_setting_source>*=’AUX’), this value will be ‘Nominal’. The nominal AGC gain values are 167 for side A and 163 for side B.
- <nh:base_agc_gain> and <nh:base_power>
The <nh:base_agc_gain> and <nh:base_power> contain the nominal/base AGC gain setting and the base/offset dBm value for the active side of the REX electronics, respectively. The base power is equivalent to the output power when RAW = (10^(-Ro/10))/Bandwidth and AGC = AGCOF, given the formula
Power[dBm] = Rbase + 10*log10(Bandwidth*RAW) + dBstep*(AGC-AGCOF) + Ro
The nominal values for this attribute are -176.852 for right circular polarization (side A) and -177.177 for left circular polarization (side B).
- <nh:radio_bandwidth>
The <nh:radio_bandwidth> attribute provides the active bandwidth of the REX radio.
- <nh:radiometry_response_step> and <nh:radiometry_response_offset>
The <nh:radiometry_response_step> and <nh:radiometry_response_offset> attributes contain the slope and intercept, for converting from raw counts to physical/ radiometric quantities. These two attributes’ values are represented by ‘dBstep’ and ‘Ro’, respectively, in the formula
Power[dBm] = Rbase + 10*log10(Bandwidth*RAW) + dBstep*(AGC-AGCOF) + Ro
- <nh:iq_calibration_constant>
The <nh:iq_calibration_constant> attribute supplies the I and Q response of the REX instrument, used to convert between raw counts and an I/Q value in mV. This constant has a nominal value of (1000 / (2^13)) mV/count.
- <nh:time_tag_calibration_constant>
The <nh:time_tag_calibration_constant> attribute provides the coefficient to be used when converting between raw counts and time tag seconds, e.g. ‘DT’ in the formula
timetag[s] = DT * RAW