| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains Voyager 1 and 2 measurements of the
brightness of Saturn at H Lyman alpha and in the H2 Lyman and
Werner bands shortward of H Lyman alpha. Pointing has been
corrected by the C-Smithing process, and these data were derived
from the pre-encounter North-South Map sequences. In this
sequence, the UVS field of view was located near the central
meridian of the planet. The field of view stepped slowly from
north to south, and then rapidly repositioned to the north.
These scans were repeated until all longitudes had been sampled.
Coverage in longitude was nearly continuous in time. There were
short breaks for observations of satellites.
The brightnesses represent integrals over the appropriate
passband that have been computed from the full spectrum. The
spectra were binned by Flight Data System (FDS) count, so that
each record contains the data from one 48-second frame.
Because the motion of the scan platform was synchronized with
FDS count, each record corresponds to a single pointing
position on Saturn. The first two spectra of each FDS count
have been excluded, because the scan platform was moving during
those times. In some cases (e.g. during the flyback slews to
prepare for another N/S scan) all spectra were flagged with bad
pointing status, and no spectra appear in the output bin. The
data in each time bin was normalized by dividing by the number
of spectra binned, so that the spectra represent counts per
3.84 second interval (the integration time in the GS-3 data
mode used for most of the encounter sequences). The final
processing step in the spectral analysis stage was a correction
for fixed pattern noise (flat fielding).
The brightnesses were computed by summing over the appropriate
wavelength channels. These are:
Voyager 1
Emission channel range wavelength range (A)
H2 bands 43 - 58 924 - 1072
H Lyman alpha 70 - 78 1174 - 1257
Voyager 2
Emission channel range wavelength range (A)
H2 bands 45 - 60 921 - 1069
H Lyman alpha 72 - 80 1171 - 1254
The brightnesses were corrected for dark counts, which arise
mainly from the radiation environment. Because the
radiation-induced dark count rate depends rather sensitively on
the magnetic latitude of the spacecraft, and hence on time,
this correction is made on a spectrum-by-spectrum basis. For
the H Lyman alpha emission, the procedure also compensates
approximately for H2 band emissions that fall within the H
Lyman alpha channel range. This correction procedure consists
of subtracting the sum over suitably chosen background
channels. These background channels are:
Voyager 1
Emission channel range wavelength range (A)
H2 bands 23 - 38 739 - 887
H Lyman alpha 58 - 66 1063 - 1146
Voyager 2
Emission channel range wavelength range (A)
H2 bands 25 - 40 736 - 884
H Lyman alpha 60 - 68 1060 - 1143
Each record contains pointing information that consists of the
latitude and SLS longitude of the two ends of the slit (P2
and P8 points) and the center of the slit (P5 point) projected
on Saturn. In addition, each point has associated with it a
status flag. A minus (-) means that the line of sight for the
specified point intersects the planet. A plus (+) means that
the line of sight is off the planet. In the latter case, the
latitude and longitude refer to the point on the planet that is
under the point of closest approach to the planet of the line
of sight.
Each logical record corresponds to one FDS count, and consists
of three lines in the data file. The quantities on each line
are:
first line: Spacecraft Event Time, FDS count, S/C to
Saturn range.
second line: P2 latitude, P2 longitude, P5 latitude,
P5 longitude, P8 latitude, P8 longitude,
P2 status, P5 status, P8 status
third line: H Lyman alpha counts, H2 band counts.
For a detailed description of the data set contents, see
[BROADFOOTETAL1981B; SANDELETAL1982; SANDEL&BROADFOOT1981; and
SMITHETAL1983].
Parameters
==========
Voyager 1 Encounter Times
-------------------------
Start Time : 1980-316/01:59:05 (1980-11-11)
Stop Time : 1980-316/12:15:04 (1980-11-11)
Voyager 2 Encounter Times
-------------------------
Start Time : 1981-236/09:02:31 (1981-08-24)
Stop Time : 1981-236/19:17:41 (1981-08-24)
Data Set Parameter 'H LYMAN ALPHA BRIGHTNESS'
---------------------------------------------
Data Set Parameter Name : H LYMAN ALPHA BRIGHTNESS
Data Set Parameter Unit : COUNTS
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND
Minimum Sampling Parameter : 48
Maximum Sampling Parameter : 48
Sampling Parameter Resolution : 48
Sampling Parameter Interval : 48
Minimum Available Sampling Int : 48
Noise Level : UNK
Data Set Parameter 'H2 BAND BRIGHTNESS'
---------------------------------------
Data Set Parameter Name : H2 BAND BRIGHTNESS
Data Set Parameter Unit : COUNTS
Sampling Parameter Name : TIME
Sampling Parameter Unit : SECOND
Minimum Sampling Parameter : 48
Maximum Sampling Parameter : 48
Sampling Parameter Resolution : 48
Sampling Parameter Interval : 48
Minimum Available Sampling Int : 48
Noise Level : UNK
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