• Exposure Time Calculator

  
  Please use the Exposure Time Calculator to estimate observing times for FUSE. This tool has been updated to provide signal-to-noise information for individual channels AND for the total (in regions of channel overlap). This link provides Instructions for Using the Exposure Time Calculator. (Note especially proper treatment of extinction correction outlined in this document!)

  Note: Many users report the best results when working on data from one channel at a time due to difficulties in wavelength solutions in overlapping regions and other non-uniformities from channel to channel. You are strongly encouraged to consider this when specifying your exposure times! (See the FUSE Observer's Guide for more information.)

• Count Rate Tool

  
  The Count Rate Tool, or the web-based simulator, can be used to estimate the total count rates from your targets. This rate is used to determine whether an observation will be completed in histogram mode or time tag mode and how much onboard memory is required to support each observation. It is a required input for each target on the Phase 2 form. This tool can also be accessed directly from within the Exposure Time Calculator.

• Blackbody UV Flux Calculator

  
  The Blackbody UV Flux Calculator is also available to estimate UV fluxes. It can be used in one of two ways: 1) using a V magnitude, E(B-V), and an effective temperature, or 2) using a blackbody curve to extrapolate from a supplied reference flux at a reference wavelength. NOTE: the calculator assumes the spectrum is a perfect blackbody and the effects of line blanketing are not included. This is NOT a high fidelity approximation of most stars, In particular, method 1 (extrapolation from V band to the far-UV) is very uncertain (especially if sources are reddened!). Hence, use this information with caution in Phase 2 inputs.

Observation Planning Tools

Following two reaction wheel failures in late 2001, and now again with another reaction wheel failure in December 2004, the FUSE attitude control system has been significantly modified to permit the continuation of the mission. The new hybrid pointing system uses the remaining reaction wheel plus the three-axis magnetic torquer bars (MTB) to control the satellite's slewing and pointing. Because the MTBs are not strong enough to allow full torque authority for all combinations of time and target position, the instantaneously available sky is more restricted than in the nominal attitude control configuration. The FUSE Sky visibility Plot is the prime tool for assessing the amount of FUSE exposure time available on a target at a particular right ascension and declination. We have retained many of the earlier tools since, for many specific applications, the information and formatted output of the earlier tools can still be useful.

• FUSE Target Visibility Tool ("VIZ") is no longer available.

  The FUSE Sky Visibility Plot is currently the prime tool for assessing the amount of FUSE exposure time available on a target at a particular right ascension and declination.

• The Slit Position Angle Calculator will calculate the beta angle (angle from antisun) and the position angle of the long dimension of the apertures on the sky for a given target as a function of date. If you plan on requesting a specific aperture position angle, you should use the calculator to ensure that the observation is feasible and find out when the angle is correct for your needs. Please note that the operational limits on beta angle for maintaining channel alignment are 30 < beta < 85 degrees! If you are primarily interested in LiF2 data, we have opened up the top range on allowed beta angle to be 115 degrees. This allows a much more effective use of the continuous viewing zone, which periodically swings to high beta angles.

• The FUSE Continuous Viewing Zone and Orbit Ram Calculator will calculate when a given target direction is in the continuous viewing zone (i.e., within 15 degrees of the orbit pole). Please note the operational limits on beta angle for channel alignment are 30 < beta < 85 degrees but beta angles up to 115 degrees are being allowed for observations requiring only the LiF2 channel. Targets with declinations below +/-45 degrees spend part of the time in the Ram avoidance zone (within +/-10 degrees of the orbital plane). The FUSE project has eliminated the Ram angle avoidance zone constraints for Cycle 8.

• The FUSE Sky Plot Tool allows the user to make CVZ or full sky plots for supplied lists of targets. Please note that this tool does not include the requirements of positive torque authority, and constraints shown have not been updated for the current range of permitted beta angles and the elimination of the Ram avoidance constraint.

General Observing Tools

• Precession Calculator
• Equatorial to Galactic Coordinate Converter
• Julian Date and Sun's Position
• Calculate the Velocity of the Local Standard of Rest

Supporting Data and Information

• FUSE Airglow Spectra
• Atomic Data and Line Lists
• Astro-1 (Dec. 1990) and Astro-2 (Mar. 1995) Hopkins Ultraviolet Telescope Reference Spectra in POSTSCRIPT format are available here for estimating FUV fluxes.
• ORFEUS I and II Spectrometer Data in POSTSCRIPT format are available here for estimating FUV fluxes.

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WebMasters: Bill Blair, Humberto Calvani
Last Update: April 8, 2005