SECCHI Synoptic and Special Observing Programs

1. SECCHI Synoptic and Special Observing Programs Simon Plunkett SECCHI Operations Lead SECCHI Consortium Meeting Orsay, France March 5-8, 2007

2. SECCHI Operations Team • S. Plunkett (Operations Lead) • N. Rich (Ground Systems Lead) • D. Wang (Flight Software Lead) • L. McNutt (Operator) • K. Battams (Operator) • E. Esfandiari (Planning/Scheduling) • R. Baugh (Program Manager) • J. Newmark (Science Planning) • You!

3. SECCHI Science Objectives

4. Concept of Operations • STEREO Mission Operations Center (MOC) is located at APL in Laurel, MD. • SECCHI Payload Operations Center (POC) is located at NRL in Washington, DC. • During commissioning and at times of emergencies, the POC will temporarily relocate to APL as necessary. • STEREO Science Center is located at NASA GSFC in Greenbelt, MD. • MOC and POC will be staffed 8 hours per day, 5 days a week, during normal business hours. • SECCHI will operate primarily in a ‘synoptic’ mode, with identical observing programs coordinated between the two spacecraft. • Additional special observations will be scheduled as needed, for example as part of coordinated campaigns. • Light travel time difference between spacecraft is handled by an adjustable constant on each spacecraft (zero for Ahead). • One ground contact period per day for each spacecraft, lasting from 3.5 to 5 hours. • Contact periods can occur at any time of the day. • Daily command loads must be prepared in advance, and delivered to MOC at least 8 hours in advance of the pass.

5. Observation Planning • Planning cycle has multiple stages, with more detailed plans established at each stage: • Quarterly SWT meetings for long-range scientific planning. • Monthly teleconferences to allocate observing sessions to specific programs. • Weekly ‘virtual meetings’ to coordinate instrument timelines and produce detailed plans. • Similar observing plan will be carried out every day in any given week: • Structures take about two weeks to cross solar disk. • STEREO spacecraft separate at about 1 degree/week. • Observing plan for one or more days is generated by the operator using the SECCHI planning tool and will be uploaded daily to both spacecraft: • Default observing program will be executed by flight software in case plan cannot be uploaded.

6. Science Constraints • Science emphasis shifts as separation angle between observatories increases. • Cannot repeat observations under the same conditions. • Requires careful planning, similar to interplanetary mission. • For example, 3D studies of coronal features using stereoscopy requires “tie-point” identification and minimization of error in height (Z) determination based upon knowledge of X-Y coordinates. • Optimal angles are between 3º < α < 15º, so needs to be done during first 6 months of mission. • Timing of CME related structures: one spacecraft sees a limb event while second spacecraft sees a disk event and halo CME. • Best suited for ~90º separation or ~ 2 years into mission. • Desire to design a mission long synoptic program that meets the top-level science objectives, while maintaining enough flexibility to evolve as separation angle increases.

7. Overlap of Views from CORs and HI1 Overlapping fields of view from the CORs and HI1 on the Ahead and Behind spacecraft about one year after launch.

8. Overlap of Views from HIs Overlapping fields of view from HI1 and HI2 on the Ahead and Behind spacecraft about one year after launch

9. 4 yr. 5 yr. 3 yr. 2 yr. Ahead @ +22/year 1 yr. Sun Sun Earth Ahead Earth 1yr. Behind @ -22/year 2yr. Behind 5 yr. 3 yr. 4 yr. Heliocentric Mission Orbit Heliocentric Inertial Coordinates (Ecliptic Plane Projection) Geocentric Solar Ecliptic Coordinates Fixed Sun-Earth Line (Ecliptic Plane Projection)

10. Spacecraft Separation Angles

11. Flight Software Constraints (1 of 2) • Only one telescope from each CEB can be in readout mode at any time. • FSW keeps a separate timeline for each CEB. • Planning Tool ensures that conflicts do not occur. • Simultaneous HI and SCIP telescope readouts are OK. • In the event that the scheduled start time of an image passes without the image being captured, the FSW will skip images until it is back on schedule. • HI summing buffers are used for summing HI image sequences. • 1024  1024 32-bit pixel buffers that hold the sum of a series of HI images. • Separate summing buffers are maintained for HI-1 and HI-2. • Up to 99 images can be summed in a sequence.

12. Flight Software Constraints (2 of 2) • Parameter tables are used to control the setup and readout of the cameras, mechanisms, exposure times and image processing parameters. • Choice of parameters is limited by the available entries in these tables. • Table entries can be changed, but this requires careful planning and configuration control to avoid conflicts. • The exposure table has 7 entries per telescope for each combination of filter/sector wheel and polarizer setting. • EUVI has 7 available exposure times for each filter/sector wheel combination. • The camera setup table includes camera gain, region of interest (image dimensions), binning, serial port clocking, waveform generator control, and waveform table. • Each telescope has 7 rows of parameters in the camera setup table. • Each telescope has 8 available CEB tables. • At least one of these tables is reserved for use as a CCD clear table. • Each telescope has 5 available occulter and region of interest masks. • These masks cannot be used with ICER compression. • The image processing table specifies processing to be applied to a raw CCD image. • IP table has 100 rows with 20 entries per row. • The same image can be processed in several ways and for several purposes, or several images can be processed only after the last is taken. • The threshold table is used for event detection to inhibit writing to the SSR2 partition. • Threshold table is derived from data from a specific telescope and should only be used with that telescope.

13. SSR Partition Management • SECCHI solid-state recorder (SSR) allocation is 6553 Mb (819 MB), divided into two science partitions and one partition for space weather beacon data. • SSR allocation for space weather beacon data is 100 Mb. • SSR1 is 80% of the total science allocation (5162 Mb): • SSR1 is intended to be used for the synoptic observing program. • SSR1 stops accepting data when full; additional data sent to this partition will be lost. • SSR1 is nominally downlinked once every day during the scheduled ground contact. • SSR2 is 20% of the total science allocation (1291 Mb): • SSR2 is intended to be used either to supplement the SSR1 synoptic program, or for special observations. • SSR2 is a circulating buffer, set to overwrite the oldest data when full, unless an event trigger is set. • SSR2 is nominally downlinked 20% every day during the scheduled ground contact  5 days required to downlink the full contents of SSR2. • All data are written to the SSR for later downlink (including real-time and space weather data).

14. Average SECCHI Daily Data Volume • Average daily data volume quoted above includes science and housekeeping data, but not space weather data. • HK data generated during the daily pass count twice, as they are sent both to the SSR and the real-time downlink channel. • Average science data volume downlinked from SSR1 during each pass is approximately 4073 Mbits. • Average daily volumes were computed prior to launch, and were based on pass durations of 3.5 hours. Actual pass durations are usually 4 hours, so a proportionally greater data volume is typically returned (after allowing for overhead at beginning and end of pass). • In reality, high data rate will probably be available for longer than 14 months.

15. SSR1 Daily Synoptic Program (Version A)

16. SSR2 Daily Synoptic Program (Version A) • EUVI observations are used to increase the image cadence in two wavelengths from 10 minutes in SSR1 to 2.5 minutes with SSR1 and SSR2 combined. • COR1 observations are interleaved with SSR1 observations for an effective image cadence of 5 minutes. • Program fills SSR2 in about 7.6 hours, after which the oldest data gets overwritten, unless an event trigger is set. • This program takes a total of 5487 images per day (SSR1 and SSR2 combined). • Some of these images are also processed for space weather.

17. SSR1 Daily Synoptic Program (Version B)

18. SSR2 Daily Synoptic Program (Version B) Does not work! • EUVI observations are used to increase the image cadence in three wavelengths from 10 minutes in SSR1 to 2.5 minutes with SSR1 and SSR2 combined, and in one wavelength from 2.5 minutes in SSR1 to 50 seconds with SSR1 and SSR2 combined. • COR1 observations are interleaved with SSR1 observations for an effective image cadence of 5 minutes. • Program fills SSR2 in about 5.8 hours, after which the oldest data gets overwritten, unless an event trigger is set. • This program takes a total of 7476 images per day (SSR1 and SSR2 combined). • Some of these images are also processed for space weather.

19. Proposed Modifications to SSR Partition Sizes • Current synoptic program assumes that average daily data volume is downlinked every 24 hours. • In reality, separation between passes can be as much as 36 hours, and frequently is at least 30 hours. • SSR allocation is sufficient for 36 hours of data at average write rates. • Since SSR1 is given higher priority than SSR2 in playback of recorder data (ratio of SSR1 packets to SSR2 packets in playback is greater than 80:20 ratio of partition sizes), SSR1 only has about 3 hours margin for separations between passes greater than nominal 24 hours. • Data will be lost with either version of this program on days when separation between passes exceeds 27 hours! • Proposed solution is to reduce size of SSR2 partition from 1291 Mbits to 800 Mbits, with this space reallocated to SSR1. • Increases margin on SSR1 to allow storage of 30 hours of data with current program. • Typical pass duration of 4 hours is sufficient to downlink all of these data (plus most of SSR2) in one pass, thus freeing up SSR space for new data.

20. Special Observing Programs • SSR2 partition is intended for special (non-synoptic) observing programs. • Possible uses include: • Increased cadence of observations already in synoptic program. • High-cadence sequences intended to capture onset of CMEs. • Observations in support of a JOP or campaign where the science objectives cannot be met with the synoptic program. • Observations to be carried out on only one spacecraft. • Remember: data on SSR2 will be overwritten once the partition is full, unless contents are frozen by an event trigger! • Remember: up to 5 days may be required to completely downlink data from SSR2 partition!

21. Joint Observing Programs • JOPs are for any instrument studies that involve special observations, from a single SECCHI telescope to campaigns involving multiple instruments or spacecraft. • Modeled on the successful SOHO JOP concept. • JOP description should be submitted to the SECCHI Science Operations Coordinator, who will evaluate the feasibility of the proposed observations. • Once accepted, JOPs will be scheduled through the normal STEREO planning process. • SECCHI Campaign in May 2007 has been written up as a JOP, including support requested from Hinode, SOHO and TRACE.

22. SECCHI Campaigns • SECCHI Campaign periods consist of an additional DSN track lasting 3.5 hours each day, beginning 12 hours after the start of the normal daily track, for a total of 4 weeks during the nominal mission. • This will enable downlink of additional SECCHI data (approximately twice the nominal daily data volume), and will enable high-cadence observations targeted to specific science objectives. • Other instruments continue to receive their normal daily data volumes. • SECCHI has planned to schedule the 4 weeks as two periods of 2 weeks each: • Campaign periods will be based on spacecraft separation angles desired for specific science objectives. • First campaign period is scheduled to occur from May 4-17, 2007, when the spacecraft are separated by about 7 degrees. • Campaign periods need to be finalized at least 6 months in advance, to allow time for scheduling of extra DSN tracks.