1. Sked: Past, Present & Future John M. Gipson NVI, Inc./GSFC 3rd IVS General Meeting Ottawa, Ontario February 9-11, 2003

2. Agenda Past—Outline of major changes Present—How it works, what it does Recent changes Future—Plans

3. Purpose of Sked Create schedules that meet the goals of the session. Take care of much of the detail work involved in scheduling a session. Allow easy creation of geodetic or astrometric schedules.

4. History 1978 Basic program created (Nancy Vandenberg) –command line input –manual selection of scans –catalogs for sources, stations, equipment 1981 Automatic calculation of antenna motion and tape handling 1988 Automatic selection of observations (Autosked) –Optimization by strict covariance. 1992 Evaluation of schedules using SOLVE simulations –Creation of pseudo-databases to evaluate formal errors. 1993 Autosked merged into standard version. –“Strange” schedules 1993 Rule based scheduling of sources. 1996 Mark IV/VLBA recording mode support added 1997 Numerous changes –Support for VEX files –Y2K fixes, –new Java-based catalog interface –S2 and K4 support

5. Sked Data Flow Master File (Experiment, date, stations) Sked Catalogs: Sources Stations Equipment … Old sked file Scheduler: Selects sources Selects recording mode. Sets scheduling parameters (SNR targets, procedures, timing) Sets optimization parameters (sky coverage, minimize slewing time, maximize observations, etc.)

6. Sked Data Flow Master File (Experiment, date, stations) Sked Catalogs: Sources Stations Equipment … Old sked file New Sked file CDDISA StationsCorrelator Schedule put on CDDISA Picked up by stations Picked up by correlator

7. Sked Data Flow Master File (Experiment, date, stations) Sked Catalogs: Sources Stations Equipment … Old sked file New Sked file CDDISA Vex file StationsCorrelator generates vex file to use in correlation

8. Sked Output General information about experiment: Sources –Flux models –Positions Station positions Antenna information –Equipment –Horizon mask Equipment –Receivers –Recorders Recording mode setup Scheduling parameters –SNR targets, maximum scan lengths –Procedure timing –Recording mode: stop& stop, continuous, adaptive. Schedule

9. Sked Modes Manual. –Scheduler chooses stations and scans –Sked has utilities for displaying whats up, etc. Automatic –Sceduler specifieds some time interval, e.g. 17:00:00 to 23:00:00 –Sked chooses scans during this interval Mixed –Automatic and manual interspersed

10. How AutoSked Works Find All Scans Start within 10 min Rank by Major Option Sky coverage Covariance Rank by Minor Options: # of Observations Rise/Set Tape Wastage … May discard some Keep best X% Keep best scan More Time? Done YesNo Compute score based on minor options

11. Recent Changes Fill in mode Best N “Astrometric” –Soft constraints to increase observing of weak sources –Won’t talk about this morning Source monitoring Common feature: Try to make sked more automatic, easier to use.

12. Fill In Mode Typical Scan for 8 station session Original Scan28 Obs=(8*7)/2

13. Fill In Mode Motivation: Minimize idle time. Typical Scan for 8 station session Strong stations finish first S S S Start End Time

14. Fill In Mode Motivation: Minimize idle time. Typical Scan for 8 station session Strong stations finish first Weak stations finish last S S S W W Start End Time

15. Fill In Mode Schedule scan using free stations Scan End Original Scan28 Obs=(8*7)/2 Fill in Scan3 Obs=(3*2)/2

16. Fill In Mode Repeat until no more idle time. Scan End Fill in Scan 2 Allowable excess Original Scan28 Obs=(8*7)/2 Fill in Scan 13 Obs=(3*2)/2 1 Obs

17. Best N: Goal Automatically choose best N sources for a session based on: –Network –Schedule start and stop times –Sky coverage –Source strength –Structure

18. Best N Algorithm 1.Find starting universe of sources: A.Read in all sources in geodetic catalog B.Read in associated fluxes C.Find all sources that are up on two or more baselines for some part of the experiment. D.Exclude sources close to the sun. 2.Rank the sources A.Schedule set of psuedo-scans that span experiment. B.Compute figure of merit for each scan: a.# of obs b.1/ (Scan Time) c.(# of obs)/(Scan time) C.Find total over all scans. 3.Combine with sky coverage to obtain final list

19. Best N Sky Coverage............. Universe of possible sources

20. Best N Sky Coverage.......A.. Start with good source A.... Highest Ranked Source

21. Best N Sky Coverage.......A.. Start with good source Add good source far from A. If several sources are similar in distance, choose highest ranking....B. Far from A.B’

22. Best N Sky Coverage.......A.C’. Start with good source Add good source far from A Add good source far from A&B If several sources are similar in distance choose higher ranked..C..B.. Far from A&B

23. Best N Sky Coverage.......A.D. Start with good source Add good source far from A Add good source far from A&B Add good source far from A&B&C … Quit when you have N-sources.C..B..

24. Source Monitoring Regular monitoring of geodetic and astrometric sources Should be (semi-)automatic Catch geodetic sources if they go bad Promote astrometric sources to geodetic if they are good Monitor stability of astrometric sources

25. Source Monitoring Lists Geodetic sources: –Current NASA catalog of 114 geodetic sources. –Goal is to observe 12/year. Astrometric sources –Defining sources in CRF –Martine’s stable sources –Martine’s sources which are not known to be unstable –About 400 sources in this list. –Observe 2/year

26. VLBI Summary Database (VSDB) For each experiment & each source: –Date –# of observations scheduled –# of observations correlated –# of observations good List of sources to monitor –Desired # of obs/year Masterfile in MYSQL format Implemented in MYSQL –Open source –Freely available –Can connect to database over net

27. Source Monitoring Dataflow SKED VSDB 1.Query database for #obs/src. Pick X underobserved sources Number of sources is user option. Typical number ~10. Sources chosen using Best N algorithm These sources are augmented from geodetic catalog using Best N. Total sources ~60.

28. Source Monitoring Dataflow SKED Schedule on CDDISA VSDB 1. Query database for #obs/src 2. Generate Schedule and put on CDDISA

29. Source Monitoring Dataflow SKED Schedule on CDDISA VSDB 3. Update VSDB NumSked NumGood=NumSked 1. Query database for #obs/src 2. Generate Schedule and put on CDDISA This is done automatically!

30. Source Monitoring Dataflow SKED Schedule on CDDISA VSDB 3. Update VSDB NumSked NumGood=NumSked Database from correlator 4. Update VSDB: NumCorr NumGood Also Automatic 1. Query database for #obs/src 2. Schedule Ready

31. Near Term Plans Better astrometric support Mark5 aware Linux What would you like?

32. Conclusions Sked is alive well Recent changes made to make it better User input always welcome