OPUS Update for April 2024 - PDS4 Support, New Ring Geometry Metadata, Display of Units

It has been awhile! For the past year and a half, we have been busy improving OPUS under the covers, and are finally ready to show off what we've done: Support for PDS4, including our first PDS4 bundle; new ring geometry metadata fields; easy selection of display units; and various other smaller improvements and fixes.

PDS4 Support

OPUS now supports PDS4! Our goal is to make PDS3 and PDS4 data sets indistinguishable to most users. Nevertheless, there are a few PDS4-specific changes:

• Everywhere OPUS used to say "Volume" it now says "Bundle/Volume". As we want to focus on PDS4 going forward, the API slug volumeid has been renamed to bundleid, although volumeid is still available for backwards compatibility.
  
• The PDS Constraints search category has renamed Data Set ID and Product ID to indicate that they are PDS3-specific fields, and added a new field Primary Product LID for PDS4 data. Since a single OPUS observation can contain many downloadable products, all of which have their own LID, we choose a "primary product" to represent the observation and allow searching on its LID. This is the same product whose filename is given in the Primary File Spec field. The field Bundle/Volume ID contains the volume name of PDS3 data and the bundle name of PDS4 data. 
• We have standardized the names of ground-based telescopes, and their abbreviations in OPUS IDs, to conform more closely to PDS4 naming standards. This has affected the PDS3 EBROCC_0001 volume in a non-backwards-compatible manner.
• We likewise have standardized the names of the DSN dishes, which are now appropriately called "DSS nnn".

Along with these PDS4 changes, we are providing our first set of PDS4 bundles - the uranus_occs_earthbased occultations of Uranus and its rings from ground-based telescopes. As with all OPUS data, we provide thumbnail diagrams to make visual searching easy, and permit selective downloading of all PDS4 products associated with each observation.

Ring Geometry Metadata Fields

Since the beginning, OPUS has provided ring longitudes referenced to the First Point of Aries, otherwise known as Right Ascension = 0. This is contrary to what many ring researchers use, which is longitudes referenced to the Ascending Node of the ring plane of the given planet at a specific epoch. We have now implemented both versions for all longitude fields, and named them explicitly to avoid further confusion. For now, the Ascending Node longitudes are computed from the RA=0 longitudes for non-occultation data sets, and the RA=0 longitudes are computed from the Ascending Node longitudes for occultation data sets, based on an approximate constant offset with an epoch during the Voyager era. As most planets precess very slowly, any errors in the conversion should be negligible. In the future, as we import fresh metadata, these values will be computed precisely.

Surface Geometry Metadata Fields

Previously, many surface geometry metadata fields that referred to values that were specific to a body's location, such as Sub-Solar Planetocentric Latitude, Sub-Observer Planetographic Latitude, or Body Center Resolution, contained only a single value in the OPUS database for each observation. However, as it is possible for these values to change over long observation periods, the database now contains minimum and maximums for these fields, as was already done for all other surface and ring geometry fields. For now, no data sets take advantage of this change, but you may notice the new min/max fields when viewing the metadata for an observation.

Selection of Display Units

Back in May 2021, we implemented units on the Search tab. Now it is also possible to select what units you want to be used when displaying metadata. This can be done from the Select Metadata dialog, and the units will be used wherever the select metadata fields are displayed (such as on the Detail tab or in slideshow mode).

Miscellaneous Changes

A few other miscellaneous changes have been made to the data:

• The Ring Geometry Constrains field Observed Resolution is now always N/A for occultations; please use Projected Radial Resolution.
• Documentation related to each mission, instrument, and data set has been added to the available download options for some data sets.
• The RMS Node-generated profile_index files for occultation data sets have been removed from the available download options, as these files are deprecated.
• The Wavelength of Cassini VIMS occultations has been corrected to be the narrowband range actually used by the occultation instead of the full available range of the instrument.

As always, we enthusiastically solicit questions and feedback from our users. And don't forget to follow us on Twitter (now X) and Mastodon for real-time updates. You can also join our low-volume announcements mailing list.