<=== observer ===>
"CLEINERT",\
"Leinert, Ch.",\
"",\
"Max-Planck-Institut f\"ur Astronomie",\
"K\"onigstuhl 17",\
"",\
"D-69117",\
"Heidelberg",\
"Germany",\
"49 6221 528264",\
"49 6221 528246",\
"leinert@mpia-hd.mpg.de"
<=== proposal ===>
"GLOBAL_4",1,1,\
{"interplanetary medium"},\
{"Salama,A.", "Gr\"un,E.", "Staude,J.", "Lemke,D.",\
"Abraham,P."}
<=== title ===>
Global mapping, seasonal variation and search for arcminute structure
of zodiacal light, Section 4
<=== abstract ===>
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
end of beta = +5.0
P_25 same 2788 s
P_60 same 2796 s
-----------------------------------------------------------
total 7992 s (2.22 h)
=== Special requirements ===
1. It is the nature of the objects studied here that they are moving with the
annual motion of the sun. This leads to the following consequences:
a. FIXED TIME OBSERVATIONS are needed in most cases, because
visibility and aspect conditions are only fulfilled around
certain dates (defined by a value of lambda(sun), but also
depending on launch date). These observations will be clearly
indicated in the object lists of the three parts of this proposal.
Typically, the time window for execution of these observations
is one or a few weeks.
b. COORDINATES in alpha, delta can and will be provided for these
moving objects, but only after more is known about
lauch date and final visibilities. Therefore they will not be given
now but after the required information is available.
c. Observations have to be performed at low background positions
and at correct angles with respect to the sun. Therefore, even for
non-fixed-time-observations strong constraints result,
and we give PREFERRED TIME WINDOWS for these observations.
2. In contrast to most other observing programmes, the measurements of this
proposal require absolute measurements. This needs both calibration and
a knowledge of the dark current of the detectors for the integration
times used. We assume, that - as part of the general calibration effort -
DARK CURRENT MEASUREMENTS of sufficient quality will be available
for the proposed measurements.
<=== scientific_justification ===>
Team top 40% middle 30% remaining 30% total performance time
---------------------------------------------------------------------
PHOT 13886 s 15369 s 10839 s 40094 s (11.2 h)
SOT 3780 s 2835 s 2835 s 9450 s ( 2.6 h)
---------------------------------------------------------------------
Sum 17666 s 18204 s 13674 s 49544 s
(4.9 h) (5.1 h) (3.8 h) (13.8 h)
36 % 37 % 28 %
=== Part 3: Search for arcminute structure ===
Three selected fields of the size of the COBE beam or, more precisely,
2x2 COBE pixels are covered by a raster scan. The observations are performed
in filter P_25, which gives maximum signal from the zodiacal light, with 4 s
integration time. Two of the fields are at high ecliptic latitude,
one is in the ecliptic plane.
The fields are to be observed on low background positions with about
| lambda - lambda(sun) | = 80.
These are FIXED TIME OBSERVATIONS WITH time windows dictated
by the visibilities.
=== Object list ===
The list is given both for an autumn launch (30.11.95) and a spring
launch (31.5.96).
object (autumn) object (spring) Observations Priority
(autumn/spring)
-----------------------------------------------------------------
ECL80,0 ECL80,0 25 micron map 2/2
ECLLOCK ECLLOCK 25 micron map 1/1
ECLMAT ECLNGP 25 micron map 3/3
-----------------------------------------------------------------
POSITIONS:
ECL80,0 is a position in the ecliptic with | lambda - lambda(sun) |
about 80 deg.
ECLLOCK is a low background position in the northern sky at about
beta =+45 deg.("Lockman hole")
ECLMAT is a low background position on the southern sky at about
beta = -40 deg.(position "EBL_22")
ECLNGP is a low background position near the north galactic pole.
VISIBILITIES:
According to presently available visibilities the following approximate
time windows result (to be updated after launch).
object autumn spring
-----------------------------------------------------------
ECL80,0 340-380 80-87,250-260,400-420
ECLLOCK,ECLNGP 160-180 180-200
ECLMA 220-240 80-87, 240-260
------------------------------------------------------------
once new information on launch date and visibility is available,
updated windows will be presented.
PERFORMANCE TIME:
Priority 1 4614 s (1.3 h)
Priority 2 4614 s (1.3 h)
Priority 3 4614 s (1.3 h)
--------------------------------------
Sum 13842 s (3.9 h)
<=== autumn_launch_targets ===>
1, "PHT05", 2.0, "N", "ECL80,0 ", 0.00000, 0.00000, 2000, 0.000, 0.000, 4614, 0
2, "PHT05", 1.0, "N", "ECLLOCK ", 10.58944, 57.51639, 2000, 0.000, 0.000, 4614, 0
3, "PHT05", 3.0, "N", "ECLMAT ", 2.10833, -28.71967, 2000, 0.000, 0.000, 4614, 0
<=== spring_launch_targets ===>
1, "PHT05", 2.0, "N", "ECL80,0 ", 0.00000, 0.00000, 2000, 0.000, 0.000, 4614, 0
2, "PHT05", 1.0, "N", "ECLLOCK ", 10.58944, 57.51639, 2000, 0.000, 0.000, 4614, 0
3, "PHT05", 3.0, "N", "ECLNGP ", 13.67306, 40.73861, 2000, 0.000, 0.000, 4614, 0