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Scheduler

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Scheduler is an application for creating observing files for all-sky pointing and other types of observations.

What it does

Scheduler basically allows you to create an observing file by graphically selecting sources that are displayed on a view of the sky. The sources are taken from a user-supplied catalog. The program accepts virtually any standard ASCII catalog. The catalog could be of radio sources, stars, asteroids,...

When you select a source, the program calculates slew times to the source, rotates the sky, and moves the telescope indicator to the source position. The user can also specify the time an observation will take which the program will use to adjust the sky view and telescope position for the end of the observation. As you select sources, an observing file is being created for you. Save the file and it's ready to be submitted to GBT Observe.

Start Up

If you are interested in trying the program out, type: 

example% cleo scheduler 

from any Linux or Sun workstation.

[The application is a stand alone utility and doesn't really need the rest of CLEO but CLEO is just a nice way of presenting the program to Green Bank users. Since it is a standalone program. the application can be wrapped up so that Windows users can simple unzip the application and run it without any M&C, Tcl, or other special software on their PC.]

For evaluation purposes, the program loads the 3CR catalog at startup.

General Features

Once you start the program, you'll find a view of the current sky on the left and a control panel on the right. Balloon help is available so if you want to know what something does, just let your mouse hover over a widget. Since the 3C catalog is pretty dense, you probably want to expand the application to take up your full screen. The color coding of the sky view's background depicts the cable wrap regions.


Now, start DOUBLE CLICKING on sources (indicated by green triangles ) in the sky and you'll see the sky and telescope (indicated by the purple target ) move to mimic the execution of an observation. In the process, you're creating an observing file!!

 

Controls

The controls for the program are located along the right hand side of the main application screen.

The green Catalog button at upper right of the main application screen will bring up a listing of the current catalog. You can DOUBLE click any source in the listing to mimic an observation of that source and add it to the observing file. It won't add sources that are below the horizon limit.


The green Observing File button at upper right will bring up a listing of the observing file you are creating. You can play back the observations, delete observations, save the file, load an existing file, etc.


Underneath these buttons you'll find checkboxes for removing certain parts of the sky view (e.g., planets, the galactic plane, labels, ....)

You can specify a range of intensities which a source must meet in order to be displayed.

For this to be a correct observing file, you should specify an observing procedure name and the time an observation will take.

If the current date and time is not appropriate for your observations, you can click the Change Date/Time button, next update the time or date, then Accept New Date/Time. Likewise, you can change the telescope's position.


At lower right of the main screen is an Options button which will allow you to configure the colors used in the display as well as telescope parameters like latitude, longitude, elevation limits, cable wrap parameters, and the equations that describe the move times. Most every Alt-Az's telescope can be configured using these settings alone so other observatories might find Scheduler useful. The default telescope settings are those of the GBT.  When you change any options, the new settings are stored in a file called .scheduler in the current working directory.  The options in this file will be used the next time you start Scheduler from that directory. 


On the sky view, you'll find widgets that will update as you move the mouse cursor over the sky. For example, you'll get an estimate of the move time from the current telescope position to where the mouse is located. Watch how the GBT cable wrap will make some moves between sources take up to 25 minutes! When you hover the mouse over a source, at the top of the screen you'll see the catalog information about the source.

Accuracies and Performance

Move times for the GBT are accurate to better than 3%.

The program does not take care of precession, nutation, aberration, .... so source Az and El's will not be accurate. Since the observing files generate Ra and Dec positions directly from catalog positions, the inaccuracies of Az and El only affect the displayed positions.

Planet positions are better than an arcmin. Sun positions to a few arcses. Moon positions to about 1/2 degree. Thus, don't count on these positions to be accurate enough for observing.

It takes about 0.5 sec on a 200 MHz Pentium PC to update the sky view. Expect the same performance on low-end Unix machines. Eliminating the display of labels, planets, Sun and Moon will improve performance. Setting an intensity range to cut back on the number of sources helps the most. 

Other Future Uses

The sky view of the application was written so that it could be encased in other Tcl applications. Other possible extensions to Scheduler are:

o Displaying the current position of the GBT.

o Move and execute an observation directly.

o Helping operators and observers determine which is the better cable wrap to specify for an observation just before the observation starts.

o As a tool for planning service/que observing.

o As an interactive exhibit in the education center allowing visitors to move the GBT model, plan pretend observations, etc.

Input Catalog and Output Files

The input catalog format is best illustrated by the comment lines we've added to the 3C catalog the program loads at startup.  

# 3rd Cambridge Catalogue of radio sources with optical identifications. Latest version after Spinrad 1990
#
# Must contain a "Fields" line which describes the data columns. Fields can be in any order. All
# but the following fields are ignored:
# name (source name)
# ra (ra in HH.hhhhh format -- if used, then cannot use rah, ram, and ras)
# ra, ram, ras (RA fields in HH MM SS format -- if used, cannot use ra)
# dec (DEC in SDD.ddddd format -- if used, cannot use decs, decd, decm, and decs)
# decsgn, decd, decm, decs (DEC in S DD MM SS format
# intensity (intensity of the source -- optional)
#
# You can preceded each catalog entry with a catalog label by including at the start of the file the
# entry "CatalogLabel: whatever". The label cannot contain embedded spaces.
#
CatalogLabel: 3C
Fields: name(1:6) rah(8:9) ram(11:12) ras(14:18) decsgn(20:20) decd(21:22) decm(24:25) decs(27:30) intensity(45:50)
2.0 00 03 48.84 -00 21 06.0 19.35* 1.037 14.9 0.67 -61 47 48 90 Q
6.1 00 13 34.48 79 00 10.4 22. 0.840 13.7 0.80 17 37 147 11 SE G
9.0 00 17 49.83 15 24 16.5 18.21 2.012 17.8 1.09 -47 53 54 11 OKE(159),SED Q
11.1 00 27 06. 63 24 00. 12.4 0.58 1 16 OBSCURED 

Thus, it should be easy to alter most ASCII catalogs for use by the Scheduler.

The output observing file currently is designed to work as a GBT Observe table.   Lines not needed by GBT Observe but needed if the file is read back into Scheduler are commented out.  Each observation takes up three lines in the output file.

# SCHED_POS: 334.678 51.036 333.560 49.327
# SCHED_TIME: 03:58:29.85 04:18:28.13 {18:11:17 05/08/2001} {18:31:12 05/08/2001} CW
3C27.0 00:52:42.00 68:13:00.0 None
# SCHED_POS: 344.507 33.071 344.921 32.441
# SCHED_TIME: 04:18:28.13 04:30:40.13 {18:31:12 05/08/2001} {18:43:22 05/08/2001} CW
3C427.1 21:04:44.80 76:21:09.5 None
# SCHED_POS: 353.447 29.697 353.931 29.465
# SCHED_TIME: 04:30:40.13 04:41:25.89 {18:43:22 05/08/2001} {18:54:06 05/08/2001} CW
3C390.3 18:45:37.57 79:43:06.5 None
# SCHED_POS: 18.570 31.447 19.046 32.191
# SCHED_TIME: 04:41:25.89 04:53:12.82 {18:54:06 05/08/2001} {19:05:51 05/08/2001} CW
3C268.1 11:57:49.89 73:17:27.5 None
# SCHED_POS: 58.708 41.808 59.498 43.948
# SCHED_TIME: 04:53:12.82 05:05:56.90 {19:05:51 05/08/2001} {19:18:33 05/08/2001} CW
3C219.0 09:17:50.70 45:51:44.2 None
# SCHED_POS: 75.059 29.934 76.566 32.196
# SCHED_TIME: 05:05:56.90 05:17:51.86 {19:18:33 05/08/2001} {19:30:26 05/08/2001} CW
3C234.0 09:58:57.38 29:01:37.4 None

The first line contains the start Az and El followed by the stop Az and El.  The second line contains the start and stop LST , start and stop UT and UT date, and cable wrap directionScheduler.  The third, uncommented line contains the source name, Ra, Dec, and observing procedure name.

 

 


Copyright 2000 Associated Universities, Inc. Washington D.C., USA
Modified: 26 September, 2001 by Ronald J. Maddalena