sked: past, present & future john m. gipson nvi, inc./gsfc 3rd ivs general meeting ottawa,...

Sked:Past, Present & Future

John M. GipsonNVI, Inc./GSFC

3rd IVS General MeetingOttawa, Ontario

February 9-11, 2003

Agenda

• Past—Outline of major changes

• Present—How it works, what it does

• Recent changes• Future—Plans

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.

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

Sked Data FlowMaster File (Experiment, date, stations)

Sked

Catalogs:SourcesStations

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.)


Sked


Equipment…

Old sked file

New Sked fileCDDISA

Stations Correlator

Schedule put on CDDISA•Picked up by stations•Picked up by correlator


Sked


Equipment…

Old sked file

New Sked fileCDDISA Vex file

Stations CorrelatorCorrelator generates vex file to use in correlation

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

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

How AutoSked WorksFind All Scans

Start within 10 min

Rank by Major Option Sky coverage

Covariance

Rank by Minor Options:# of Observations

Rise/SetTape Wastage

…

May discard some

Keep best X%

Keep best scan

More Time? DoneYes No

Compute scorebased on

minor options

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.

Fill In Mode

Typical Scan for 8 station session

Original Scan 28 Obs=(8*7)/2

Fill In Mode

Motivation: Minimize idle time.Typical Scan for 8 station session

Strong stations finish first

S

S

S

Start EndTime

Fill In Mode

Motivation: Minimize idle time.Typical Scan for 8 station session

Strong stations finish firstWeak stations finish last

S

S

S

W

W

Start EndTime

Fill In Mode

Schedule scan using free stations

Scan End


Fill in Scan 3 Obs=(3*2)/2

Fill In Mode

Repeat until no more idle time.Scan End

Fill in Scan 2Allowable excess


Fill in Scan 1 3 Obs=(3*2)/21 Obs

Best N: Goal

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

Best N Algorithm

1. Find starting universe of sources:A. Read in all sources in geodetic catalogB. Read in associated fluxesC. 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 sourcesA. Schedule set of psuedo-scans that span

experiment.B. Compute figure of merit for each scan:

a. # of obsb. 1/ (Scan Time)c. (# of obs)/(Scan time)

C. Find total over all scans.3. Combine with sky coverage to

obtain final list

Best N Sky Coverage

.

. .

.

.

.

.

.

.

.

.

..

Universe of possible sources

Best N Sky Coverage

.

. .

.

.

.

.A

.

.

Start with good source A

.

.

..

Highest Ranked Source

Best N Sky Coverage

.

. .

.

.

.

.A

.

.

Start with good sourceAdd good source far from A.

•If several sources are similar in distance, choose highest ranking.

.

.

.B. Far from A.B’

Best N Sky Coverage

.

. .

.

.

.

.A

.C’

.

Start with good sourceAdd good source far from AAdd good source far from A&B

•If several sources are similar in distance choose higher ranked.

.C

.

.B..

Far from A&B

Best N Sky Coverage

.

. .

.

.

.

.A

.D

.

Start with good sourceAdd good source far from AAdd good source far from A&BAdd good source far from A&B&C…Quit when you have N-sources

.C

.

.B..

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

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

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

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 algorithmThese sources are augmented from geodetic catalog using Best N.Total sources ~60.


SKED

Schedule on CDDISA

VSDB

1. Query database for #obs/src

2. Generate Schedule and

put on CDDISA


SKED

Schedule on CDDISA

VSDB

3. Update VSDBNumSked

NumGood=NumSked

1. Query database for #obs/src

2. Generate Schedule and

put on CDDISA

This is done automatically!


SKED

Schedule on CDDISA

VSDB

3. Update VSDBNumSked

NumGood=NumSked

Database from correlator

4. Update VSDB:NumCorrNumGood

Also Automatic1. Query database

for #obs/src

2. Schedule Ready

Near Term Plans

• Better astrometric support• Mark5 aware• Linux• What would you like?

Conclusions

• Sked is alive well• Recent changes made to make

it better• User input always welcome

sked: past, present & future john m. gipson nvi, inc./gsfc 3rd ivs general meeting ottawa,...

Documents