TIPS Meeting

1. TIPS Meeting 19 December 2002, 10am, Auditorium Observing Solar System Objects with JWST Ed Nelan COS - Updates on COS Development Ken Sembach NICMOS Status Tommy Wiklind Next TIPS Meeting will be held on 16 January 2003.

2. Observing Moving Targets with JWST Ed Nelan TIPS Dec 19, 2002

3. Observing Moving Targets with JWST Ed Nelan TIPS Dec 19, 2002 Ron Henry, Wayne Kinzel, Andy Lubenow, Knox Long, Vicki Balzano, Larry Petro, John Isaacs, Mark Abernathy, Rusty Whitman, Bill Workman

4. Moving Targets • Observations of moving targets with JWST is not part of the baseline plan. • Currently, there is no requirement for JWST to track a moving target • The STScI proposal for the JWST Science & Operations Center (S&OC) does not include support for observations of moving targets. • Science Working Group's interest in Solar System objects motivated a study by STScI to estimate the cost to the for supporting such observations.

5. Moving Targets • Cost estimates in this study are for the Ground System (S&OC), i.e., STScI, only. • Cost for flight software development not included. • We did not investigate if JWST can track moving targets, or the cost in doing so (TRW) • We did not estimate the additional cost for FGS FSW (CSA) • Can the Science Instruments observe the bright planets? • We did not address the cost for SI modifications(SI teams)

6. Moving Targets • Moving Targets are Solar System bodies: • Kuiper Belt Objects • planets • moons of planets • asteroids • comets • Compared to stars, they are nearby, and they move • JWST parallax • ephemeris

7. Moving Targets Outline of this presentation: • Why observe moving targets with JWST ? • What angular rates might be encountered? • Costs: • Observatory efficiency, scheduling • Operations, proposal preparation, planning & scheduling ($) • Software development, I&T, maintenance ($$)

8. Why Observe Moving Targets?Shoemaker-Levy 9

9. Why Observe Moving Targets?Shoemaker-Levy 9 and Jupiter Impacts

10. Why Observe Moving Targets? • Between 1994 and 1996 ~35% of all HST public out reach releases involved Solar System observations. • But only ~2% of the HST program was dedicated to Solar System observations.

11. What’s involved inMoving Target Observations? • Fixed targets (stars, galaxies, e.g.) are stationary with respect to the guide star. • A Solar System object moves with respect to a guide star • Proposal Preparation, Planning & Scheduling: • Ephemeris • JWST parallax • Tracking. • Complicates selection of the guide star

12. Fixed Target Observations * Fixed target * Science Instrument FGS

13. Moving Target Observations * Moving target * * Science Instrument FGS

14. At what angular speeds doSolar System bodies travel? From J. Nella,JWST kickoff Meeting, 10/23/02

15. Angular rates of Neptune within JWST FOR 1 mas / sec

16. Angular rates of Jupiter within JWST FOR 5 mas / sec

17. Angular rates of Mars within JWST FOR 25 mas / sec

18. Angular rates of selected objects within JWST FOR * Includes motion about Pluto-Charon barycenter

19. Moving Target Observations may requirelong guide star track lengths * Moving target * * Science Instrument FGS

20. Moving Target Observations may requireshort guide star track lengths * Moving target * * Science Instrument FGS

21. Proposal Preparation, Planning and Scheduling • The position of a Solar System object on the celestial sphere as seen from JWST will depend upon the the spacecraft’s position in its orbit about L2. • Orbit has a radius of 800,000km • Period of about 120 days. • S/C’s predicted position will be uncertain by TBD% when forecast one year in advance (proposal preparation time). • Station keeping maneuvers difficult to predict. • Implications for S&OC’s generation of LRP. • To investigate, we assumed 10% ephemeris uncertainty.

22. gs2 JWST in L2 Orbit gs1

23. gs2 JWST in L2 Orbit gs1

24. gs2 JWST in L2 Orbit gs1

25. gs2 JWST in L2 Orbit gs1

26. JWST in L2 Orbit gs Not a problem with HST in low orbit, Earth’s ephemeris is well known.

27. Proposal Preparation, Planning and Scheduling Uncertainty of a Solar System object’s position as seen by JWST due to a 10% error in spacecraft’s one year predicted ephemeris.

28. Proposal Preparation, Planning and Scheduling • If bad pixels in FGS cause loss of lock on guide star: • need an accurate ephemeris to verify the path of a guide star across the FGS while JWST tracks target is free of bad pixels. • If the FGS can guide across bad pixels: • the uncertainty of the JWST predicted ephemeris is unlikely to present a major problem (proposals can be flight ready many months in advance) • Uncertainty in long range forecast of spacecraft ephemeris might delay final selection of a guide star until a few months before observations occur. Impacts LRP.

29. Observatory Efficiency, Event Driven Schedule flexible constrained Plan window Visit duration

30. Visit with long plan windowHDF

31. Visit with short plan window1.5 hours after SL-9 Impact

32. JWST Event Driven Schedule Will observations of moving targets cause a loss of observatory efficiency? • Observations will execute as visits within plan windows. • Plan windows will overlap in time. • Each plan window contains only 1 visit. • Ideal Plan window is long compared to the visit duration. • Visits execute at the earliest time possible. • This approach minimizes gaps in observatory activities

33. JWST Event Driven Schedule • Overlapping Plan windows allow observations to execute according to events, and not be restricted to absolute times. Visit 1 Visit 2 Visit 3 Visit 4 time

34. JWST Event Driven Schedule • If visit 2 fails, visit 3 executes early. No idle gap, observatory efficiency preserved. Visit 1 Visit 2 Visit 3 Visit 4 time

35. JWST Event Driven Schedule • If visit 2 fails, visit 3 executes early. No idle gap, observatory efficiency preserved. Visit 1 Visit 2 Visit 3 Visit 4 time

36. JWST Event Driven Schedule • If visit 2 fails, visit 3 executes early. No idle gap, observatory efficiency preserved. Visit 1 Visit 2 fails Visit 3 executes early Visit 4 executes early time

37. JWST Event Driven Schedule • When time constrained observations populate the schedule, loss of observatory efficiency can result if failures occur Visit 1 Visit 2 Visit 3 Visit 4 time

38. JWST Event Driven Schedule • When time constrained observations populate the schedule, loss of observatory efficiency can result if failures occur Visit 1 Visit 2 Visit 3 Visit 4 time

39. JWST Event Driven Schedule • When time constrained observations populate the schedule, loss of observatory efficiency can result if failures occur Visit 1 Visit 2 Visit 3 Visit 4 time

40. JWST Event Driven Schedule • When time constrained observations populate the schedule, loss of observatory efficiency result when failures occur. Visit 1 Visit 2 Visit 3 gap Visit 4 time

41. Distribution of target-local HST plan windows for Solar System targets, 2000-2002

42. Visit with short plan window1.5 hours after SL-9 Impact

43. Visit with long plan windowSaturn

44. JWST Event Driven Schedule Observations of most Solar System objects can be scheduled when required tracking rates are very low. • If guide star availability is the only constraint, visits can have long plan windows, and flexible scheduling. • If target-local considerations determine plan window, restrictive scheduling results. • Visits cause loss of efficiency when visits upstream in the queue fail. Same as time constrained observations of fixed targets. • Degradation of observatory efficiency due to Solar System observations not expected to be significant.

45. JWST Event Driven Schedule Suppose all visits to all targets are of the same length and • JWST spends 3% of its time observing solar system targets, • And 20% of these observations are time constrained, • And only 10% of all observations upstream in the queue (including fixed targets) fail. • Then the loss of observatory efficiency due to time constrained (Solar System and fixed target) observations is, assuming all visits are of the same length; 0.03  0.2  0.1 = 0.0006 = 0.06 %

46. Proposal Preparation, Planning and Scheduling

47. Cost to S&OC for Observing Solar System Bodies • To facilitate costs analysis: • adopted an operations concept • identified requirements levied on the ground system and flight software to implement concept. • estimated $$ cost to meet the requirements. • estimated the cost for daily operations. • The $$ cost to the S&OC is dominated by software development needed for the proposal preparation, planning, and scheduling systems.

48. Observing moving targets with JWSTConcept Assumptions • All observatory level restrictions applied to fixed targets apply to moving target observations. • Science instrument modes and target acquisition schemes used for fixed targets will suffice for moving target observations. • JWST can track targets using an ephemeris. • Only one guide star used for a visit. It shall be within the same FGS detector for the duration of the plan window.

49. Observing moving targets with JWST • Concept supports observations of any moving target. Flight software and hardware set the limits. • Concept is similar to HST approach, but is consistent with event driven schedule architecture. • Concept is not optimized for observations when the guide star availability time is less than the time required to gather the science data (fast comet). • Get science by scheduling multiple visits with short plan windows, each with new guide star. • Operations impact might be acceptable if instances are rare.

50. Observing moving targets with JWST • For economy we assumed maximum re-use of the HST moving targets ground system (APT, MOSS) • ~500,000 lines of code!!! • Concept results in ~12% increase in the size of APT, the Planning & Scheduling System, and the Guide Star Selection System.