Data Set Information
|
DATA_SET_NAME |
ESO22M SR AP-PHOTOMETER RESAMPLED RING OCCULTATION V1.0
|
DATA_SET_ID |
ESO22M-SR-APPH-4-OCC-V1.0
|
NSSDC_DATA_SET_ID |
PSRI-00005
|
DATA_SET_TERSE_DESCRIPTION |
ESO 2.2 meter telescope data from
|
DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains stellar occultation data from the 1989
occultation of 28 Sagittarii (28Sgr) by Saturn obtained by the 2.2
meter telescope (ESO22M) at the European Southern Observatory.
Data include occultation profiles for both ingress and egress
which each cover a radial slice from the outer edge of Saturn's
atmosphere to beyond the orbit of the F-ring.
Ring profiles are archived as resampled normal optical depth
profiles. Geometry solutions and noise models are also provided.
Parameters
==========
The data were obtained at 3.4 microns, using InSb nitrogen-
cooled aperture photometer in the chopping mode. The chopping
frequency was 8.8 Hz with a 98-arcsec E-W throw. The effective
focal ratio was f/35, and 5-arcsec diaphragms were used to
minimize background noise. Data were recorded digitally at 100 Hz.
Processing
==========
No information is available concerning the preliminary reduction
of the data.
The fully processed and resampled ring profiles have been
generated as follows:
(1) Observations of the 28 Sgr occultation made from several
observatories were combined with Voyager PPS and RSS data sets
to determine precisely the ring radial scale and the Saturn pole
orientation (FRENCHETAL1993, HUBBARDETAL1993,
NICHOLSONETAL2000).
(2) Using the improved ring radial scale, the time-series of raw
samples was converted to a uniformly-spaced series of radial
samples. The spatial sampling interval used was 10 km,
corresponding to Nyquist-sampled data based on the apparent star
diameter of approximately 18 km.
(3) Raw data DN levels were converted to normalized flux based
on the viewing geometry, and subsequently to normal optical
depth.
Data
====
The resampled data are presented in seven column ASCII tables.
The columns are (1) radius(km), (2) normalized flux, (3) sigma
flux, (4) normal optical depth(tau), (5) tau lower, (6) tau
upper, (7) quality flag.
The quality flag has five possible values. They are: 0=ok, 1=tau
greater then tau_max, 2=non-photometric, 3=corrupted data,
4=missing data. For detailed discussion of the model used to
determine noise and reasonable values for optical depth see
MODEL.TXT in the DOCUMENTS sub-directory.
In general, for corrupted or missing data, dummy values of
9.9990 are used in columns 3-6.
Ancillary Data
==============
Browse data (BROWSE/ESO22M sub-directory)
-----------------------------------------
This subdirectory contains two types of plot for each
observation run.
Plots of radial profiles of stellar flux normal optical depth of
the rings as derived from the observations of the 28 Sgr
occultation by the rings of Saturn. Each plot is based on the
corresponding profile data file in the corresponding
subdirectory of the DATA directory.
Plots of ancillary geometry information. Each plot is based on
the corresponding profile data file in the corresponding
subdirectory of the GEOMETRY directory.
Geometry information (GEOMETRY/ESO22M sub-directory)
----------------------------------------------------
The geometry information is provided in separate files for
ingress and egress. Data are arranged in four columns:
a) Equatorial Radius (Km),
b) Observatory received time (UTC),
c) Ring Plane inertial longitude of the intercept point (deg),
d) delta time (s). The latter is a correction factor used when
determining the line-of-sight distance between the ring
intercept point and the observer. The data are presented
with uniformly varying radius (1000 km increments) between
73,000 km and 142,000 km.
The data are arranged in the order of increasing radius
regardless of whether the observation is ingress or egress.
Geometry data were obtained using a polynomial fit. The
polynomial coefficients can be found in DOCUMENTS/POLY_CO.TXT
Coordinate System
=================
All geometric quantities appearing in the labels are in J2000
coordinates. In this coordinate frame, the z-axis points
northward along the Earth's J2000 rotation axis and the x-axis
points toward the First Point of Aries. In some cases, B1950
coordinate values are also included.
Media/Format
============
This data set is archived on compact disc (CDROM) media.
Organization and formats are according to PDS and ISO 9660
level 2 standards.
Most binary data files are in least-significant-byte first, which
is the native format for PCs and Digital workstations. Users of
Suns and other workstations may need to swap bytes in some data
files before use. Note that the software tools provided on this
volume swap the bytes automatically if this is necessary.
|
DATA_SET_RELEASE_DATE |
2004-03-30T00:00:00.000Z
|
START_TIME |
1989-07-03T04:00:00.000Z
|
STOP_TIME |
1989-07-03T10:00:00.000Z
|
MISSION_NAME |
SATURN OCCULTATION OF 28 SAGITTARIUS 1989
|
MISSION_START_DATE |
1989-07-03T12:00:00.000Z
|
MISSION_STOP_DATE |
1989-07-03T12:00:00.000Z
|
TARGET_NAME |
SATURN
S RINGS
|
TARGET_TYPE |
PLANET
RING
|
INSTRUMENT_HOST_ID |
ESO22M
|
INSTRUMENT_NAME |
APERTURE PHOTOMETER
|
INSTRUMENT_ID |
APPH
|
INSTRUMENT_TYPE |
PHOTOMETER
|
NODE_NAME |
Planetary Rings
|
ARCHIVE_STATUS |
ARCHIVED
|
CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
Overall the confidence level is high. Flawed data are clearly
identified by non-zero values for the quality flag.
Observing conditions were good throughout the occultation: the
average seeing was 1.2 arcsec in the visible and 1.4 arcsec in the
infrared; signal quality was good throughout much of the event.
However, signal quality was substantially degraded by the end of
the occultation due to drifting of the star out of the small
aperture. There is evidence of timing problems; consequently these
observations should be treated as providing accurate relative
measurements of the times of ring features, but not accurate
absolute ring event times.
Peer Review
===========
Peer review of this data set was completed in February 2005. The
peer reviewers were Shawn Brooks (JPL), Richard G. French
(Wellesley College), Colleen A. McGhee (Wellesley College), Cathy
Olkin (South West Research Institute), and Leslie Young (South
West Research Institute). The data set was also reviewed at the
PDS Engineering Node by Steven L. Adams.
Data Coverage and Quality
=========================
Observing conditions were good throughout the occultation. The
average seeing was 1.2 arcsec in the visible and 1.4 arcsec in the
infrared. Atmospheric immersion occurred during the C Ring
occultation, commingling ring features with the spikes in the
atmosphere occultation light curve. Nonetheless, identifiable ring
features could be measured throughout most of the ingress and
egress occultations.
There is some evidence of timing problems with this data set.
These observations should be treated as providing accurate
relative measurements of the times of ring features, but not
accurate absolute ring event times. For a more detailed
discussion, see FRENCHETAL1993.
|
CITATION_DESCRIPTION |
French, R.G., P.D. Nicholson, and M.K. Gordon, Radial Profiles of
Saturn's Rings from the ESO 2.2 Meter Telescope Observations
of the 1989 Occultation of 28 Sgr, ESO22M-SR-APPH-4-OCC-V1.0,
USA_NASA_PDS_EBROCC_0001, NASA Planetary Data System, 2003.
|
ABSTRACT_TEXT |
not applicable
|
PRODUCER_FULL_NAME |
MITCHELL K. GORDON
|
SEARCH/ACCESS DATA |
Rings Node Interface
Rings Online Archives
|
|