JWST General Target Visibility Tool Help
The JWST General Target Visibility Tool (GTVT) is a command-line Python tool that provides quick-look assessments of target visibilities and position angles for all JWST instruments.
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See also: JWST Moving Target Visibility Tool Help, JWST Position Angles, Ranges, and Offsets, JWST Observatory Coordinate System and Field of Regard
The JWST General Target Visibility Tool (GTVT) is a Python command-line tool for calculating target visibility windows as a function of time. GTVT is one of 2 primary tools for investigating JWST target visibilities.
For a given RA and Dec, the GTVT provides the reference position angle (PA) information for all 4 science instruments and the FGS within the allowed visibility windows. It also outputs the V3 axis PA for reference. Results are in the form of an ASCII file as well as one or more summary plots. A number of options are available from the command line for tailoring the output to your needs. Once the interactive plot is displayed, icons can be selected to pan and zoom in on the plot to see detailed information.
The GTVT contains an optional branch that permits the easy inclusion of moving targets instead of just fixed coordinate targets. See JWST Moving Target Visibility Tool Help for more information on this option.
The schedulability of a given target observation is more complex than just its visibility. It also involves the availability of guide stars as a function of time and other constraints that may be set with special requirements in APT. The GTVT is a "quick look" tool for pre-planning purposes, but the Astronomers Proposal Tool is the true arbiter of schedulability for a given proposed observation.
Dependencies
Words in bold are GUI menus/
panels or data software packages;
bold italics are buttons in GUI
tools or package parameters.
pip install [PACKAGE]
command (where PACKAGE is one of the dependencies listed above) to assess whether it is installed. If not already installed, the pip command will do so.
Installation and usage
The GTVT is currently incompatible with Windows operating systems.
One can download a .zip file or clone the repository for GTVT from the following GitHub link:
https://github.com/spacetelescope/jwst_gtvt
and install the tool inside the resulting jwst_gtvt-master directory (you should see a file called setup.py in this directory) with the command
python setup.py install
Alternatively, if you are familiar with pip, you can install the tool directly with
pip install jwst_gtvt
or
pip install git+https://github.com/spacetelescope/jwst_gtvt.git
These options assume you have separately verified that your computer has access to the dependencies listed above. Once successfully installed, the program can be run from the command line, as described in the next section.
Usage tips
To see the GTVT help information, type jwst_gtvt -h.
usage: jwst_gtvt [-h] [--v3pa V3PA] [--save_plot SAVE_PLOT] [--save_table SAVE_TABLE] [--instrument INSTRUMENT] [--name NAME]
[--start_date START_DATE] [--end_date END_DATE] [--no_verbose]
ra dec
positional arguments:
ra Right Ascension of target in either sexagesimal (hh:mm:ss.s) or degrees.
dec Declination of target in either sexagesimal (dd:mm:ss.s) or degrees.
options:
-h, --help show this help message and exit
--v3pa V3PA Specify a desired V3 (telescope frame) Position Angle.
--save_plot SAVE_PLOT
Path of file to save plot output.
--save_table SAVE_TABLE
Path of file to save table output.
--instrument INSTRUMENT
If specified plot shows only windows for this instrument. Options: nircam, nirspec, niriss, miri, fgs, v3
(case insensitive).
--name NAME Target Name to appear on plots. Names with space should use double quotes e.g. "NGC 6240".
--start_date START_DATE
Start date for visibility search in yyyy-mm-dd format. Earliest available is 2021-12-26.
--end_date END_DATE End date for visibility search in yyyy-mm-dd format. Latest available is 2024-10-02.
--no_verbose Suppress table output to screen
GTVT command line examples
When using GTVT in the command line, you only need to specify RA and Dec (the default input values). Observability windows are shown on the terminal, and plots of visibility windows for each instrument are displayed. However, there are other useful command-line options, as shown in the examples below; each command is followed by a text description.
jwst_gtvt 325.678 43.586 --name "SS Cyg"
This command runs and produces an interactive visibility plot on the screen for all instruments. No files are saved to disk. Note that enclosing the target name in double quotes allows for spaces in the text. To exit the program, close the plot window. Alternatively, if you want access to the terminal window from which the tool was run prior to exiting the program, add an ampersand "&" at the end of the command-line entry above to run the program in the background.
jwst_gtvt 325.678 43.586 --name "SS Cyg" --save_plot SSCyg_all.png
This command only saves a plot to a file; no interactive plot is displayed.
jwst_gtvt 325.678 43.586 --name "SS Cyg" --instrument v3 --save_plot SSCyg_v3.png
This command shows a single instrument panel for (in this case) the V3PA. The allowed values for --instrument are "nircam", "nirspec", "niriss", "miri", "fgs", and "v3" (case insensitive). To exit the program, close the plot window.
jwst_gtvt 325.678 43.586 --name "SS Cyg" --save_table SSCyg.dat
The command produces a plot on the screen for all 6 instruments. Tabular data are sent to a file instead of being displayed on the screen. To exit the program, close the plot window.
jwst_gtvt 325.678 43.586 --name "SS Cyg" --save_plot SSCyg_all.jpg --save_table SSCyg1.dat
This command saves both outputs to the specified files; there is no interactive plot.
jwst_gtvt 325.678 43.586 --name "SS Cyg" --start_date 2022-07-01 --end_date 2023-06-30
An interactive plot is displayed for all 6 instruments, starting at July 1, 2022 and running for one year. To exit the program, close the plot window.
The example below shows the top portion of an ASCII output file from a simple run of GTVT. The top section provides a summary of the target and windows, and the bottom table (truncated) shows the day-by-day minimum and maximum allowed angles in each of the visibility windows for each instrument. The nominal angles are approximately midway between the 2 limits shown.
ecliptic
RA Dec latitude
325.678 43.586 52.656
Checked interval [2021-12-26, 2024-10-02]
| Window [days] | Normal V3 PA [deg] |
Start End Duration Start End RA Dec
2022-06-02 2022-12-20 201.07 243.68898 50.62431 325.67800 43.58600
2023-06-02 2023-12-21 201.99 243.89490 50.12458 325.67800 43.58600
2024-06-02 2024-10-02 121.10 243.35636 124.30248 325.67800 43.58600
V3PA NIRCam NIRSpec NIRISS MIRI FGS
Date min max min max min max min max min max min max
2022-06-03 240.06 247.16 239.96 247.07 18.63 25.73 240.62 247.73 244.90 252.00 238.82 245.92
2022-06-04 238.94 246.76 238.84 246.66 17.50 25.32 239.50 247.32 243.77 251.59 237.70 245.51
2022-06-05 237.81 246.35 237.72 246.25 16.38 24.92 238.38 246.91 242.65 251.19 236.57 245.11
2022-06-06 236.69 245.95 236.60 245.85 15.26 24.51 237.25 246.51 241.53 250.78 235.45 244.70
2022-06-07 235.57 245.54 235.48 245.45 14.14 24.11 236.13 246.10 240.41 250.38 234.33 244.30
2022-06-08 234.69 244.90 234.60 244.80 13.26 23.47 235.26 245.46 239.53 249.74 233.45 243.66
2022-06-09 233.94 244.14 233.84 244.04 12.50 22.71 234.50 244.70 238.77 248.98 232.70 242.90
2022-06-10 233.18 243.38 233.08 243.28 11.75 21.95 233.74 243.94 238.01 248.22 231.94 242.14
2022-06-11 232.42 242.62 232.32 242.53 10.99 21.19 232.98 243.18 237.26 247.46 231.18 241.38
2022-06-12 231.66 241.86 231.57 241.77 10.23 20.43 232.23 242.43 236.50 246.70 230.42 240.62
2022-06-13 230.91 241.11 230.81 241.01 9.47 19.67 231.47 241.67 235.74 245.94 229.67 239.87
2022-06-14 230.15 240.35 230.05 240.26 8.72 18.92 230.71 240.91 234.99 245.19 228.91 239.11
2022-06-15 229.39 239.60 229.29 239.50 7.96 18.16 229.95 240.16 234.23 244.43 228.15 238.36
2022-06-16 228.63 238.84 228.54 238.74 7.20 17.41 229.19 239.40 233.47 243.68 227.39 237.60
2022-06-17 227.87 238.09 227.78 237.99 6.44 16.65 228.43 238.65 232.71 242.92 226.63 236.85
2022-06-18 227.11 237.33 227.01 237.24 5.68 15.90 227.67 237.89 231.95 242.17 225.87 236.09
2022-06-19 226.35 236.58 226.25 236.48 4.92 15.14 226.91 237.14 231.19 241.41 225.11 235.34
2022-06-20 225.59 235.82 225.49 235.72 4.15 14.39 226.15 236.38 230.42 240.66 224.35 234.58
2022-06-21 224.82 235.07 224.72 234.97 3.39 13.63 225.38 235.63 229.66 239.90 223.58 233.83
2022-06-22 224.06 234.31 223.96 234.21 2.62 12.88 224.62 234.87 228.89 239.15 222.81 233.07
2022-06-23 223.29 233.55 223.19 233.46 1.85 12.12 223.85 234.11 228.12 238.39 222.05 232.31
2022-06-24 222.52 232.79 222.42 232.70 1.08 11.36 223.08 233.36 227.35 237.63 221.28 231.55
2022-06-25 221.75 232.04 221.65 231.94 0.31 10.60 222.31 232.60 226.58 236.87 220.50 230.79
2022-06-26 220.97 231.28 220.87 231.18 359.54 9.84 221.53 231.84 225.81 236.11 219.73 230.03
2022-06-27 220.19 230.51 220.10 230.42 358.76 9.08 220.76 231.07 225.03 235.35 218.95 229.27
2022-06-28 219.41 229.75 219.32 229.65 357.98 8.32 219.98 230.31 224.25 234.59 218.17 228.51
2022-06-29 218.63 228.98 218.53 228.89 357.20 7.55 219.19 229.55 223.47 233.82 217.39 227.74
2022-06-30 217.85 228.22 217.75 228.12 356.41 6.78 218.41 228.78 222.68 233.05 216.61 226.98
2022-07-01 217.06 227.45 216.96 227.35 355.62 6.01 217.62 228.01 221.89 232.28 215.82 226.21
2022-07-02 216.27 226.68 216.17 226.58 354.83 5.24 216.83 227.24 221.10 231.51 215.03 225.43
2022-07-03 215.47 225.90 215.37 225.80 354.04 4.47 216.03 226.46 220.31 230.74 214.23 224.66
2022-07-04 214.67 225.12 214.58 225.03 353.24 3.69 215.23 225.69 219.51 229.96 213.43 223.88
2022-07-05 213.87 224.35 213.77 224.25 352.44 2.91 214.43 224.91 218.71 229.18 212.63 223.10
2022-07-06 213.06 223.56 212.97 223.47 351.63 2.13 213.63 224.12 217.90 228.40 211.82 222.32
2022-07-07 212.25 222.78 212.16 222.68 350.82 1.34 212.82 223.34 217.09 227.61 211.01 221.54
2022-07-08 211.44 221.99 211.34 221.89 350.01 0.55 212.00 222.55 216.28 226.82 210.20 220.75
2022-07-09 210.62 221.20 210.52 221.10 349.19 359.76 211.18 221.76 215.46 226.03 209.38 219.95
2022-07-10 209.80 220.40 209.70 220.30 348.36 358.97 210.36 220.96 214.63 225.24 208.56 219.16
2022-07-11 208.97 219.60 208.87 219.50 347.54 358.17 209.53 220.16 213.80 224.44 207.73 218.36
2022-07-12 208.14 218.80 208.04 218.70 346.70 357.36 208.70 219.36 212.97 223.63 206.90 217.56
...(full table truncated)
Example plots from GTVT
By default, a plot showing 6 panels (one for each instrument, the FGS, and the observatory V3PA) will be displayed by GTVT on the screen or sent to a named output file. The y-axis of each plot shows valid aperture PAs for each instrument as a function of time. These values can be entered into the relevant APT special requirements as needed for a given science case.
This summary plot may not be that useful when saved as a file. But in interactive mode, icons at the lower left of the plot window allow you to pan and zoom within each panel for a closer look at the figures. After panning and zooming in the interactive plot, the right-most icon provides another way to save the current view of the interactive plot.
Alternatively, for viewing a single instrument, use the --instrument argument to specify a particular instrument; this produces a display with a single panel plot for that instrument. Also, the time range on the default plot covers the entire current period with a preliminary orbital ephemeris. You can also use the --start_date and --end_date arguments to shorten the time range that is plotted. Figure 2 shows an example made with the following command:
jwst_gtvt 325.678 43.586 --name "SS Cyg" --instrument nirspec --start_date 2022-07-01 --end_date 2023-01-31
Additional information on JWST’s pointing restrictions, and how those affect target visibility and available position angles are included in the article JWST Position Angles, Ranges, and Offsets.