Web Interface

The Web-based tool, Viewing, consists of three components, in addition to the user interface. These components are

• the name resolver,
• the command-line program, viewing, and
• the XMM-Newton Visibility Tool.

Viewing is a Web interface for the viewing command-line utility developed by Dr. Koji Mukai. It calculates the seasonal viewing windows, as determined by the Sun angle constraints of various observatories. Viewing can also provide visibility window restrictions due to the angle with respect to the Moon, which is currently implemented for Swift, NICER, and NuSTAR. Orbital pole restrictions have also been implemented for Swift. A target near of the orbital poles of the Swift orbit will violate its Earth constraint at all times. We provide the approximate times when such a target is too close to the orbital pole, based on an extrapolation of the Swift orbit. More precise Swift constraints are available from the Swift MOC within ~10 days of an observation, using the up-to-date ephemeris for the satellite's orbit. More precise NuSTAR constraints are also available from the NuSTAR Constraint Checker.

Given the nature of the tool, it should be used only to check for the approximate visibility windows. Internally, the Sun angle is calculated in 1-day steps, which limits the accuracy of the results. For time-critical observations near the edge of a viewing window, consult the respective mission for authoritative limits.

In the case of XMM-Newton, for which other constraints play an essential role, we have incorporated the visibility tool written by the XMM-Newton SOC.

The range of dates checked by the Web interface goes from the current date to two years in the future. That applies to all missions supported by Viewing except for XMM-Newton, whose range can vary from one to two years.

This integrated Web version of the Viewing Tool was developed and is maintained by Edward J. Sabol.

Command-Line Interface

Version 3.4 of the command-line tool, viewing, is available from

https://heasarc.gsfc.nasa.gov/FTP/software/tools/

Download the files viewing3_4c.tar.gz and viewing_install.guide.

Usage:

viewing [mission=<name>/range=n1-n2] [equinox=year] [from=dd-mmm-yy] [for=y.y / to=dd-mmm-yy] [input=<file>] [output=<file>]

or

viewing none

The command-line tool was developed and is maintained by Dr. Koji Mukai.

For feedback or questions concerning Viewing, please contact Edward J. Sabol and Dr. Koji Mukai.