1. SOC-Provided Ancillary Data: Update
Andrew Walsh, Chris Watson, Marc Costa

2. What Does Ancillary Data Mean?
In this context:
Time Conversion
Orbit
Attitude
Coordinates Systems, Reference Frames, Fields of View
Operational Misalignments
How we will produce these:
Primarily SPICE Kernels
Limited CDF ‘Digests’
Described in Draft TN:
SOL-SGS-TN-0017
SOC-Provided Ancillary Data for Solar Orbiter [PDF]

3. SPICE Kernels SPICE = Software toolkit provided by NAIF/JPL/NASA.
Kernels = Data files for SPICE software.
Well-used in solar system missions & very well documented here.
These will be the primary ancillary products.
Use them for anything operational and important.
Produced by SOC with support from ESA SPICE Service.
Follows our naming conventions first, PDS second.
If you have questions about SPICE for Solar Orbiter in the first instance contact me and/or
Primarily delivered to SGS via GFTS.

4. Progress Since SOWG9
Production of draft kernel dataset (on Confluence here, 25MB zip).
Fictional Spacecraft Clock
Orbit
Predicted Attitude kernels (default so far, no rolls)
Spacecraft and instrument reference frame kernels
Draft Instrument fields of view
Draft scientific reference frames kernel
Definition of approach to metakernels and versioning.
Definition of kernel production approach within SOC.
Webgeocalc instance and Cosmographia configuration
Thanks to Marc Costa for doing most of the work!

5. Progress Since SOWG9
Production of draft kernel dataset (on Confluence here, 25MB zip).
Fictional Spacecraft Clock
Orbit
Predicted Attitude kernels
Spacecraft and instrument reference frame kernels
Draft Instrument fields of view
Draft scientific reference frames kernel
Definition of approach to metakernels and versioning.
Definition of kernel production approach within SOC.
Webgeocalc instance and Cosmographia configuration
Thanks to Marc Costa for doing most of the work!

6. Progress Since SOWG9
Production of draft kernel dataset (on Confluence here, 25MB zip).
Fictional Spacecraft Clock
Orbit
Predicted Attitude kernels
Spacecraft and instrument reference frame kernels
Draft Instrument fields of view
Draft scientific reference frames kernel
Definition of approach to metakernels and versioning.
Definition of kernel production approach within SOC.
Webgeocalc instance and Cosmographia configuration.
Thanks to Marc Costa for doing most of the work!

7. Implemented Reference Frames & Attitude
"J2000" INERTIAL |
ck->| "SOLO_PRF"(1)
|<-ck ck->| <-fixed
| |
V V
"SOLO_INS_BOOM" "SOLO_FOF" .
V V V
Individual instrument frame trees
Spacecraft and instrument frames in solo_ANC_soc-sc-fk_V00.tf
Some frames are defined entirely in this file, others need a separate attitude kernel (ck) in order to be used.
Science frames in a separate kernel.

8. Implemented Reference Frames & Attitude
"J2000" INERTIAL |
ck->| "SOLO_PRF"(1)
|<-ck ck->| <-fixed
| |
V V
"SOLO_INS_BOOM" "SOLO_FOF" .
V V V
Individual instrument frame trees
SOLO_PRF = spacecraft coordinates
Can be oriented slightly differently relative to J2000 depending on which ck is loaded:
Orbit normal, ecliptic normal, equator normal attitude options all implemented.
Default is currently orbit normal.
6 monthly cks with comms rolls etc. coming soon.

9. Implemented Reference Frames & Attitude
"J2000" INERTIAL |
ck->| "SOLO_PRF"(1)
|<-ck ck->| <-fixed
| |
V V
"SOLO_INS_BOOM" "SOLO_FOF" .
V V V
Individual instrument frame trees
Some instrument frames are defined as fixed relative to spacecraft coordinates.
E.g. EPD sensors, PAS, HIS

10. Implemented Reference Frames & Attitude
"J2000" INERTIAL |
ck->| "SOLO_PRF"(1)
|<-ck ck->| <-fixed
| |
V V
"SOLO_INS_BOOM" "SOLO_FOF" .
V V V
Individual instrument frame trees
Others are fixed relative to intermediate, ck-based frames.
SOLO_INS_BOOM = Instrument boom frame
MAG, RPW-SCM, defined relative to this. EAS TBD.
Allows us to take into account non-optimal boom orientations.
(If we can figure out what they are through data analysis later)

11. Science Frames
First Draft Science Frames kernel ready for review: solo_ANC_soc-sci-fk_V00.tf
The following frames have been implemented:
SOLO_SUN_RTN Sun Solar Orbiter Radial-Tangential-Normal
SOLO_SOLAR_MHP S/C-centred mirror helioprojective
SOLO_IAU_SUN_ Sun Body-Fixed based on IAU 2009 report
SOLO_IAU_SUN_ Sun Body-Fixed based on IAU 2003 report
SOLO_GAE Geocentric Aries Ecliptic (GAE)
SOLO_GSE Geocentric Solar Ecliptic (GSE)
SOLO_HEE Heliocentric Earth Ecliptic (HEE)

12. Science Frames
First Draft Science Frames kernel ready for review: solo_ANC_soc-sci-fk_V00.tf
The following frames have been implemented:
Heliocentric generic frames(*):
SUN_ARIES_ECL Geocentric Aries Ecliptic (HAE)
SUN_EARTH_CEQU Heliocentric Earth Equatorial (HEEQ)
SUN_EARTH_ECL Heliocentric Earth Ecliptic (HEE)
SUN_INERTIAL Heliocentric Inertial (HCI)
Geocentric Generic Frames(*):
EARTH_SUN_ECL Geocentric Solar Ecliptic (GSE)
EARTH_MECL_MEQX Earth Mean Ecliptic and Equinox of date frame (Auxiliary frame for EARTH_SUN_ECL)
These frames may be implemented by NAIF, if so we’ll remove them.

13. Ecliptic-Based Science Frames
In our definition of ecliptic-based frames (GSE, HEE, ecliptic default attitude) we were planning to use the ecliptic of J2000.
The NAIF definition that will soon go into their ‘standard’, built in science frames kernel uses the ecliptic-of-date.
We don’t have a strong feeling which is better.
Does anyone have a preference?
If not, we suggest to follow the NAIF definition and adopt ecliptic-of-date.

14. Instrument Kernels Contain rudimentary FoV information only.
We don’t want these to be used as repositories of information about the instruments as in some planetary missions.
We also don’t want these to be needed by end users to analyse the data (as in some planetary missions) your science data should contain all of the necessary metadata, following the solar orbiter metadata standard.

15. Metakernels
Metakernels define a self-consistent set of other kernels so you can just load one file and be sure you have everything you need.
SOC will maintain two metakernels, one for predictive files, one for as-flown.
This is primarily because of the dependency between attitude kernels and the spacecraft clock.
It also has the advantage of keeping a clean separation between different uses of the files, reducing the possibility of confusion.
It has the disadvantage of meaning that for visualisation tools you may need to switch between predictive and historic ‘modes’ by loading a different kernel set.
Metakernels will also be our primary means of versioning the kernel dataset.
A new metakernel will be issued whenever any other new kernel is produced.

16. Kernel Versioning
Some of our kernels will be produced manually every so often:
E.g. reference frames, orbit, fields of view.
Others will be produced automatically more frequently (usually based on telemetry)
E.g. flown attitude, spacecraft clock…
A new version of the kernel dataset will be issued whenever new manual files are produced (e.g. a change in the operational misalignment of an instrument).
This will be tracked using the version of the metakernel:
e.g. solo_ANC_soc-pred-mk_V010_ _001.tm

17. Kernel Versioning
Some of our kernels will be produced manually every so often:
E.g. reference frames, orbit, fields of view.
Others will be produced automatically more frequently (usually based on telemetry)
E.g. flown attitude, spacecraft clock…
A new version of the kernel dataset will be issued whenever new manual files are produced (e.g. a change in the operational misalignment of an instrument).
This will be tracked using the version of the metakernel:
e.g. solo_ANC_soc-pred-mk_V010_ _001.tm
The date of production of the file is intended to show the most recent automatically-generated kernel included, to give an idea of coverage.

18. Homework For us (by the SWT in October):
Update the ancillary data tech note to reflect these latest developments.
For you (by the next SOWG):
Please review your instruments’ frames and fields of view.
Is everything named as you’d like?
E,g, EPD EPT-HET are currently ned EPT-HET-MY and EPT-HET-PY not 1 & 2. Is this ok would you prefer 1 and 2?
Are the frames correctly defined? (we’ve used the Airbus frames TN as a source)
Please play around with the kernels and see if you spot anything odd.
Bear in mind these are drafts, so don’t use them for anything (too) important.

19. Cosmographia & WebGeoCalc Demo