Contents of: VI/111/./abstract/CLEINERT_GLOBAL_1.abs

The following document lists the file abstract/CLEINERT_GLOBAL_1.abs from catalogue VI/111.
A plain copy of the file (without headers/trailers) may be downloaded.


SCIENTIFIC ABSTRACT

The purpose of this proposal is twofold. First, to provide a global
 picture of the zodiacal light as seen by ISOPHOT. This skeleton allows
 us to make consistent use of the large amount of serendipity background
 measurements to be expected; it allows us to adopt the results obtained with
 the infrared satellite COBE for use or comparison with ISO; it helps to
 determine reliable backgrounds, which is important in particular
 for studies of galactic and extragalactic background, but also for
 the study of faint objects. Second, it allows us to study aspects of
 the spatial distribution of interplanetary dust which have not been
 treated sufficiently so far: the search for arcminute structure in the
 zodiacal light, the out-of-ecliptic distribution, the variation of
 absorption cross section per unit volume with heliocentric distance,
 and the location of the plane of symmetry as a function
 of heliocentric distance, where distance is measured by the temperature
 of the dust. For these measurements the ability of ISO to avoid stars and
 bright infrared cirrus and therefore to measure "pure" zodiacal light, is
 an important advantage.
This proposal is part of the ISOPHOT effort to measure diffuse sky
brightness. It is coordinated in some detail with the ISOPHOT proposals
"Measurement of the extragalactic background radiation", "Properties of
interplanetary dust" and "Diffuse infrared emission of the galaxy".





=== summary === 

OBSERVATION SUMMARY
  The distribution and absolute brightness  of zodiacal light is studied by
means of multiband photometry. There are three parts to this proposal:

	1. To determine the global distribution of zodiacal light
	2. To measure the seasonal variations of the zodiacal light
	3. To search for arcminute structure in the zodiacal light

The first two parts will be performed in sufficient extent to allow
an intercomparison with COBE and use of the COBE results for inter-
polation. The choice of filters has been coordinated with the
proposal on "extragalactic backgound light", to which the zodiacal
light constitutes an important foreground. The filter at 180 micron
is most sensistive to cirrus emission and is always included to
improve the correction for this emission.
  We aim at relative photometric accuracies of a few percent or better,
which is needed to separate extragalactic background light from the much
brighter zodiacal light and which is highly wanted for modelling of the
interplanetary dust distribution.
Object lists and breakdown of observations by AOT's will be given in the
three separate parts. The common observing plan for photometry
will be given in this summary. For all measurements the largest
available aperture (180 arcsec) will be used.


PERFORMANCE TIME OVERVIEW

    Observations          priority 1   priority 2   priority 3   sum
    ----------------------------------------------------------------------------
    global mapping            -        13590 s      9060 s     22650 s  (6.3 h)
    seasonal variation     21066 s       -            -        21066 s  (5.9 h)
    arcminute structure     4614 s      4614 s      4614 s     13842 s  (3.9 h)
    ---------------------------------------------------------------------------
    total                  25680 s     18204 s     13674 s     57558 s
                                                                  
                           (7.1 h)      (5.1 h)    (3.8 h)    (16.0 h)
                            45 %         32%         24%


=== Detailed observing plan ===

1. Wideband photometry

           Filter      t(on object)     t(performance)  
           -------------------------------------------------
           P_3.6          256 s             562 s        
           P_7.3           32 s             114 s        
           P_11.5          32 s              98 s        
           P_25            32 s             198 s        
           P_60            32 s             200 s        
           C_160           32 s              76 s        
           C_180           32 s              82 s        
	   Acquisition                      180 s 
           -------------------------------------------------
           Performance time                1510 s    (0.42 h)


2. Mid-IR photometry

           Filter      t(on object)     t(performance)   
           -------------------------------------------------
           P_12.8          32 s             106 s        
           P_25            32 s             198 s        
           P_60            32 s             200 s        
           C_180           32 s              82 s        
	   Acquisition                      180 s
           -------------------------------------------------
           Performance time                 766 s    (0.21 h)



3. "Slew" photometry

         filter            " slew "            performance time
         -----------------------------------------------------------
         P_11.5      start beta = -5.0            2408 s
                     four sparse maps, each about
                     2.5 deg          

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