1. WFIRST-AFTA Ops Concept Overview DRAFT 1

2. Multiple surveys with different requirements to implement the various science programs –High Latitude Survey (HLS): ~2,400 deg 2 imaging and spectroscopic sky survey for BAO/RSD & WL (dark energy science), also used for archival studies by guest investigators –Supernova (SN) Survey: Multiple visits to SN fields at high ecliptic latitudes to discover and track SN (dark energy science) –Exoplanet Microlensing Survey: Multiple visits to microlensing fields near Galactic bulge to monitor planetary microlensing events –Exoplanet Coronagraph Survey: Observe nearby stars to find and characterize both previously known and new planets –Guest Observer: Allocated time for proposers to observe targets anywhere within the field of regard Survey Strategy 2

3. The high latitude, supernova, and exoplanet microlensing surveys will all use the wide field instrument –HLS imaging survey uses the wide field imager –HLS spectroscopy survey uses the wide field grism –SN survey uses the wide field imager for discovery and the wide field IFU to type SN, measure redshifts, and obtain lightcurves –IFU may also be used in parallel with HLS imaging or spectroscopy to support photometric redshift calibration –Microlensing survey uses the wide field imager The exoplanet coronagraph survey uses the coronagraph instrument –Imager is for finding planets and for photometric characterization and the IFS is for spectroscopic characterization The guest observer program can use either instrument The wide field instrument will operate during coronagraph observations –Needed for fine guiding, but will also take deep imaging exposures Coronagraph observations are not currently planned during wide field instrument observations –Are there reasons to leave the coronagraph powered on during wide field observations for thermal or reliability reasons? Implementation of Surveys 3

4. The HLS covers ~2,400 deg 2 over ~2 years in both imaging (~1.3 yrs) and spectroscopy (~0.6 yrs) modes and is spread out over the 6 year mission HLS footprint is in regions of high Galactic latitude and is within the LSST footprint (or other deep visible survey) for photometric redshifts. In imaging mode, perform 2 passes over the survey footprint in each of the 4 imaging filters (J,H,F184 [for shapes] and Y [for photo-z’s] –There is a “leading” and “trailing” pass in each filter to provide roughly 180˚ roll (but exactly 180˚ not desired) for data set self-calibration (current ops plan has ~150˚, will be optimized later) –Each pass includes four ~184 sec exposures (with five exposures in the J band, since we are attempting WL shape measurement in this band and it has the tightest sampling requirements) –Each exposure is offset diagonally by ~slightly more than a chip gap. This pattern is repeated across the sky in both the X and Y directions spaced by the field size. –90% of imaging field sees ≥5 randomly dithered exposures (≥920 sec total) in Y, H, F184 bands, ≥6 exposures (≥1104 sec total) in J band –No requirement on roll alignment between passes in different filters In spectroscopy mode, perform 4 passes total over the survey footprint –The grism has 2 “leading” passes and 2 “trailing” passes to provide roughly 180˚ roll (but exactly 180˚ not desired) to enable the single grism to rotate relative to the sky and provide counter- dispersion (current ops plan has ~150˚, will be optimized later) –Each pass includes two ~362 sec exposures with a small offset to cover chip gaps –The 2 “leading” passes (and 2 “trailing”) are rotated from each other by ~5˚ –90% of spectroscopy field sees ≥6 randomly dithered exposures (≥2172 sec total) –Zero order galaxy provided in J,H or J,F184 bands by WL imaging passes There is no direct requirement for absolute pointing accuracy (either initial or revisit). The chief consideration is minimizing the overlap of adjacent fields needed to avoid gaps in the survey. An absolute pointing accuracy corresponding to 1% of the size of an SCA (~4.5 arcsec) is a representative value. High Latitude Survey 4

5. HLS (Imaging) Mapping (view in slide show mode) 5 Perform 1 st pass mapping of a super field in the 1 st filter 4 exposures with a gap filling offset between each Perform 1 st pass mapping of a super field in the 1 st filterPerform 1 st pass mapping of a super field in the 2 nd filterPerform 1 st pass mapping in the remaining two filtersPerform 2 nd pass mapping in the 1 st filter ~6 months (or N years + 6 months) later Perform 2 nd pass mapping in the 2 nd filter ~6 months (or N years + 6 months) later Perform 2 nd pass mapping in the remaining 2 filters ~6 months (or N years + 6 months) later

6. HLS (Spectroscopy) Mapping (view in slide show mode) 6 Perform 1 st pass of a super field 2 exposures with a gap filling offset Perform 2 nd pass of a super field at a slight rollPerform 3 rd pass of a super field ~6 months (or N years + 6 months) later Perform 4 th pass of a super field at a slight roll ~6 months (or N years + 6 months) later

7. The Type Ia supernova survey observes for a total of 6 months but is carried out over a total of 2 years in separate 1-year periods. The imager is used for SN discovery and the IFU spectrometer is used to type SN, measure redshifts, and obtain lightcurves Supernova observations take place with a five-day cadence, with each interval of observations taking a total of 30 hours of combined imaging and spectroscopy. Fields are located in low dust regions ≤20˚ off an ecliptic pole Example 3-tiered survey with each tier optimized for a different redshift range –Tier 1 for z<0.4: 27.44 deg 2 in Y and J bands –Tier 2 for z<0.8: 8.96 deg 2 in J and H bands –Tier 3 for z<1.7: 5.04 deg 2 in J and H bands –Tier 3 is contained in Tier 2 and Tier 2 is contained in Tier 1 Need SN mapping strategy –Gap filling –Revisit accuracy TBD –Dither with 30 mas accuracy IFU exposure times are tailored for each individual supernova Final revisit for each target for spectroscopy after SN fade for galaxy subtraction, some may occur after the dedicated 2 year period, but are accounted for in the example observing scenario Weekly interaction with the ground after visiting discovery fields to schedule follow ups on SN candidates Type Ia Supernova Survey 7

8. Supernova Field Mapping 8

9. Example Weekly Discovery and Follow up Timeline 9 SunMonTuesWedThursFriSat 3/4 Day Cadence 5 Hour SNe Discovery 2 Hour Candidate SN Spectroscopic Follow-Up Data Downlink/Uplink Data Downlink Only Weekly Obs. & New SNe Spec. Obs. Prior concept for slit spectrometer ops on JDEM Probe. I expect there will be a similar plan for discovery and follow up with an IFU, but need inputs from SN group.

10. The exoplanet microlensing survey observes 10 fields in the Galactic bulge for continuous 72-day seasons, interrupted only by monthly lunar avoidance cutouts (~4 days/month). The plan includes 6 seasons, with >2 years between the first and last season. The Galactic Bulge is observable for two 72-day seasons each year. In each season, the 10 fields are revisited on a 15 min cadence, viewing in a single wide filter (W149) for light curve tracking. For one exposure every 12 hours, a narrow, blue filter (Z087) is used to measure the color of the microlensing source star. Fields are revisited to an accuracy of ~110 mas (1 pixel rms) TBD; no precise dithers Data latency for notifications to other assets? Exoplanet Microlensing Survey 10

11. Detecting Planets with a Microlensing Survey 11

12. Current example observing schedule has observations scheduled in 26 blocks of 2 weeks each, interspersed throughout the mission. Portions of each block are dedicated to detecting a planet (imaging) and characterizing a planet (spectroscopy). The targets are around nearby stars (within ~10 parsecs) and are distributed around the field of regard. The current operations planner assesses the availability of each potential target star during each block of coronagraph observing time. Out of a catalog of 239 potential target stars, in each of the 26 coronagraph observing blocks we find at least 24 to be continuously viewable over the full 2-week period with no violations of the Earth, Moon, or Sun pointing constraints. Exoplanet Coronagraph Survey 12

13. Acquire a dark hole on a nearby bright star –Acquire star in tip/tilt –Measure and remove low order WFE –Measure and remove high order WFE –Verify dark hole Slew to target star –Thermal loads change in this process Acquire target –Imager is coarse sensor –LOWFS is the fine sensor –Apply tip/tilt control to set the target on occulter –1 st order correction of low order wavefront Integrate –Each band and each sensor Strawman Observing Scenario 13

14. Allocated time throughout the 6-year mission for proposers to observe targets anywhere within the field of regard The GO program by definition cannot be “allocated” at this stage in the project. The scheduling of HLS observations can be re-organized based on the content of the GO program. Currently, we have simply required that the time not used for other programs be ≥1.25 years, and that all portions of the sky are visible in multiple years during otherwise-unallocated time. –In computing the unallocated time, we subtract the penalty for a typical 90° slew from each unallocated window. (This way, the slewing penalty between any two programs is charged against the time allocation of one of the programs but not both.) Guest Observer Program 14

15. Central Line of Sight (LOS) Field of Regard (FOR) 15 +54˚ Keep-Out Zone Observing Zone Keep-Out Zone SNe Fields +126˚ Galactic Bulge (Available twice yearly) SNe Fixed Fields be ±20˚ off one of the Ecliptic Poles, Microlensing can observe Inertially Fixed Fields in the Galactic Bulge (GB) for 72 days twice a year WL/ BAO-RSD/ GO/Coronagraph Surveys can be optimized within the full Observing Zone Observing Zone: 54˚-126˚ Pitch off Sun Line 360˚ Yaw about Sun Line ±15˚ Roll about LOS (off max power roll) GB The LOS cannot point within 33° (TBR) of the limb of the Earth and 8° (TBR) of the Moon.

16. Galactic Bulge Viewing 16 Looking down on the ecliptic plane, ~72 day seasons available to view the bulge Galactic Bulge 36˚ Ecliptic Plane Galactic Plane Galactic Bulge

17. Observing timeline with constraints in GEO orbit; initial inclination 28.5°, initial RA of ascending node 228° (over 6 years, precesses to inclination=26.4°, RAAN=188°). Example Observing Schedule 17

18. This timeline is an existence proof only, not a final recommendation. Unallocated time is 1.43 years (includes GO program) High latitude survey (HLS: imaging + spectroscopy): 1.96 years –2401 deg 2 @ ≥3 exposures in all filters (2440 deg 2 bounding box) 6 microlensing seasons (0.98 years, after lunar cutouts) SN survey in 0.62 years, field embedded in HLS footprint 1 year for the coronagraph, interspersed throughout the mission Example Observing Schedule: Properties 18 High Latitude Survey Area Microlensing Fields Ecliptic Plane Celestial Equator

19. 1.2 Gbps continuous Ka downlink capability from GEO –Preliminary analysis indicates at least 16x microstepping required to keep jitter down during observations –Wide Field Instrument produces ~600 Mbps, assumes 2x lossless compression –Coronagraph data volume 30 Gbits/day plus <1 Gbits/day LOWFS 2 Ka antenna on-board, only one radiating at a time Ground architecture similar to SDO –2 ground stations at White Sands, both within the beam width of the Ka antenna Downlink 19

20. Slew/settle accuracy for each program (when can we start next obs) FGS ops Orbit maintenance Momentum unloading Ground system –Assumes MOC is 8x5 Additional Info to Include 20

21. Blind Acquisition – No guide stars picked out Directed Acquisition – Pre-planned guide stars Field – The projected field of view on the sky Super Field – Multiple deg 2 portion of the sky mapped at one time Slews –Dither –Gap filling –X-Field –Y-Field Frame Time – The length of time to read out a single detector Integration Time – The effective observation time between the first and last read frame of each pixel in a detector without any resets in between. Definitions 21

22. Continuous Viewing Zone Analysis 22

23. Baseline Cycle 4 orbit is circular GEO –Initial inclination = 28.5˚, RAAN = 236˚ –Precession (perturbations from Sun, Moon, and Earth oblateness through ℓ=4) Field of regard –Pitch range ±36˚ (angle from Sun = 54-126˚) –Telescope LOS to Earth center ≥ 41.7˚ (TBR) (33˚ (TBR) from Earth limb from Len Seale’s stray light analysis + 8.7˚ Earth radius) –Chris ignored the Moon for this analysis (moves at 13˚/day, can avoid with minimal impact) –No constraints on radiator angles Eclipses –Earth eclipse seasons at  <9˚ –Also 15 Moon eclipses outside these seasons in 6 year mission (short, can avoid – not discussed here) Sky Availability-Basic Assumptions (courtesy Chris Hirata) 23

24. Earth Cutouts 24

25. Earth Cutout Geometry 25

26. Sun Cutouts 26 +54˚ Keep-Out Zone Observing Zone Keep-Out Zone SNe Fields +126˚ Galactic Bulge (Available twice yearly) GB

27. Combined Cutouts 27

28. Beta Angle over the Mission 28

29. Fraction of Sky Available versus  29

30. The following 7 charts show the combined Earth + Sun viewing constraints at 1 month intervals. The Sun viewing constraint is periodic every 6 months since the pitch limit is symmetric under positive pitch (away from Sun, up to +36˚) and negative pitch (toward Sun, down to -36˚). Thus the last chart is the same as the first. In each hemisphere, the region between the gray curves is allowed by the Sun, and within the blue circles is allowed by the Earth. Maximum viewing fraction (satisfying both constraints) is at low  (April or October). Combined Cutout Charts 30

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