GALEX Mission Planning Target Visibility Plot (GMPS)  Karl Forster July 2007
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The GALEX Mission Planning System (MPS) generates a plot showing the
availability of eclipses where it is safe to observe a target. For
cycle 4 of the GALEX Guest Investigator program (GI4) the target viability
is determined for the period 2007 December 31st to 2009 February 8th.

The angle between the target position (telescope boresite) and the
list of reference bodies given below is calculated for every eclipse
in GI4. Angles must be greater then the following or a violation is
recorded.

Sun > 85 degrees
Moon > 25 degrees
Earth center > 98 degrees (this also covers the bright Earth limb)
Mars, Jupiter, Saturn > 2 degrees
Ram direction (direction of orbital motion) > 40 degrees

Eclipses were no violations occur within the period of the eclipse are 
considered to be viable for mission planning of the target. It is possible
for a target to have no viable eclipses in GI4.

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The GMPS plot has three sections.

Top section: - Plots the visibility of eclipses for the proposed target.

  The date is printed above the plot and vertical red dashed lines
  indicate month boundaries (e.g. January 1st 2008, February 1st 2008... 
  February 1st 2009).  The horizontal axis is the eclipse number
  (eclipse 1 was on the first orbit after launch (April 28th 2003).

  The target proposal ID and target number are printed in the top left.

  Eclipses that are viable are indicated by a vertical gold stripe. In
  general groups of eclipses will be viable so these periods will appear
  as gold rectangles.

  The total number of viable eclipses is printed on the right side of
  the plot.

  The viable eclipse with the minimum zodiacal light is marked with a
  blue arrow pointing down and the maximum with a green arrow pointing
  up.

  Eclipses where the total NUV brightness for the detector is violated
  have the bottom half of the gold stripe over-plotted with green hash
  marks.

Middle section: - The variation in zodiacal light for the target.

  The NUV count rate expected from zodiacal light foe every eclipse is
  plotted as the green line. The scale is 1000 NUV counts/s. The bottom
  axis is eclipse number and matches the axis of the top section of the
  plot.

  The vertical red dashed month boundaries continue from the top section
  as do the markers for the minimum (blue) and maximum (green) zodiacal
  light for viable eclipses.

  The default zodiacal light level for the brightness checker tool on
  the guest investigator website was 20000 NUV counts/s and this is
  marked on the plot as a horizontal blue dashed line.

  The maximum allowable zodiacal light level for the target is marked on
  the plot as a horizontal pink dashed line. This is calculated from the
  total NUV count rate expected from the stars in the GALEX field of
  view, the count rate expected from diffuse galactic emission for the
  target and the count rate limit for the NUV detector (50000 counts/s).
  I.e.

    Max Zodiacal Light = 50000 - stars - diffuse galactic emission


Bottom section: - Text information about the target and MPS calculations

  The eclipse range and date range for the plot are indicated below the 
  zodiacal light plot.

    Target ID: The proposal ID and target number
    Plan ID:   Used for mission planning (ignore)
    Type:      All targets have type GII (ignore)
    RA:        Target Right Ascension (degrees)
    Dec:       Target declination (degrees)

    Min Planned Exposure: Proposed total exposure time for the target
    Accumulated Exposure: Is zero for all targets (ignore)
    Max Zodiacal Light:   See above.
    Eclipse Available:    The total number of viable eclipses and the
                          percentage of the total number of eclipses in
                          GI4.

  The eclipse and date at which the minimum and maximum zodiacal light
  for viable eclipses is printed along with the expected NUV count rate
  due to zodiacal light.

    Diffuse Galactic Emission: The expected NUV DGE for the target

    Stars in FOV:  The expected NUV count rate from cataloged stars in  
                   the field of view.

    Total Flux Range: The range in total expected NUV count rate from 
                      minimum to maximum zodiacal light.

    Remaining Eclipses Available: The number of viable eclipses minus  
                                  the number of viable eclipses where 
                                  the total NUV count rate exceeds the 
                                  50000 counts/s limit.

  If the total NUV count rate for the eclipse with the minimum (maximum)
  zodiacal light exceeds the count rate limit then the Min (Max)
  Zodiacal flux, the Total Flux Range, and Remaining Eclipses Available
  are printed in red.