PDS_VERSION_ID = PDS3
LABEL_REVISION_NOTE = "SFH 2006-09-27
2012-09-14 SBN:T.Barnes Removed DATA_SET_ID.
2017-02-24 CG/CT: removed wrong info in INSTRUMENT_DESC and refer to Keller et al."
RECORD_TYPE = STREAM
OBJECT = INSTRUMENT
INSTRUMENT_HOST_ID = "RO"
INSTRUMENT_ID = "OSINAC"
OBJECT = INSTRUMENT_INFORMATION
INSTRUMENT_NAME = "OSIRIS - NARROW ANGLE CAMERA"
INSTRUMENT_TYPE = "FRAME CCD REFLECTING TELESCOPE"
INSTRUMENT_DESC = "
The instrument was provided by the OSIRIS consortium led by the
principal investigator Dr. Horst Uwe Keller.
The OSIRIS consortium have the following members:
MPS Overall responsibility and project management, system
engineering, interfaces, Focal Plane Assemblies, CCDs
and Readout Boards, HK Boards, integration and
qualification of E-Boxes, harnesses, system
integration, high level software, NAC & WAC system
calibration, QA, mission operations
LAM NAC telescope, camera integration and qualification
WAC optical bench, camera
UPD Integration and qualification, shutter mechanisms and
shutter electronics, Front Door Mechanisms (mechanisms
for NAC and WAC)
IAA Mechanism Controller Board
INTA Filter Wheel Mechanisms, E-Box Power Converter Module,
NAC & WAC CRB Power Converter Modules
RSSD Data Processing Unit
IDA Mass memory, low level software and data compression
DASP NAC & WAC Filters
UPM Thermal and structural analysis, NAC MLI, WAC FPA MLI
For detailed instrument description please see the Space Science
Review Paper by Keller et al. (2007) included in the dataset
(DOCUMENT/OSIRIS_SSR/KELLER_ET_AL_2007_V01.PDF).
OSIRIS, the Optical, Spectroscopic, and Infrared Remote Imaging
System is the scientific camera system on board Rosetta. It
comprises a Narrow Angle Camera (NAC) and a Wide Angle Camera (WAC)
with a field of view (FOV) of 2.20 degree times 2.22 degree and
11.35 degree times 12.11 degree, respectively, and an
instantaneous field of view (IFOV) of 18.6 microradian per pixel
and of 101.0 microradian per pixel, respectively. Both cameras use
a 2048 times 2048 pixel backside illuminated CCD detector with a
UV optimized anti-reflection coating. The CCDs are equipped with
lateral anti-blooming that allows overexposure of the nucleus
without creating saturation artifacts, enabling the study of
details in the faint coma structures next to the illuminated limb.
The CCD full well capacity is smaller than 120000 electrons per
pixel (Keller et al. 2007). The pixel linearity is guaranteed only
below this limit. A gain value of 3.1 electrons per DN (DN =
digital number) in HIGH gain mode and 15.5 electrons per DN in LOW
gain mode is used, as specified by the manufacturer. Calibration
images to measure the gain were acquired in December 2014, and
will be used to investigate whether an update to the current gain
values is needed. The NAC and WAC are equipped with two readout
ampli?ers each that can be used independently or together to
achieve a faster readout of the image. Both cameras are off-axis
systems, with no central obscuration along the beam. The off-axis
design has the advantage of providing high transmittance from the
UV to the near-IR and diffraction limited performance with low
geometrical optical aberration, but introduces a significant
geometric distortion that needs to be corrected for scientific use
of the image products.
The NAC is equipped with 11 filters covering a wavelength range of
250 nanometer to 1000 nanometer, while the WAC has 14 filters
covering a range of 240 nanometer to 720 nanometer. The
transmission curves of the NAC and WAC filters can be found in
Figure 1 of Tubiana et al. 2015 included in the dataset
(DOCUMENT/CALIB/TUBIANA_ET_AL_2015_V01.PDF).
In addition to the bandpass filters, the NAC filter wheels contain
a neutral density filter and anti-reflection coated focus plates:
three far focus plates (FFP-UV, FFP-VIS, and FFP-IR) and a near
focus plate (NFP-VIS). The focus plates, combined with the
bandpass filters, allow two focusing ranges: far focus from
infinity to 2 kilometer, optimized at 4 kilometer, and near focus
from 2 kilometer to 1 kilometer, optimized at 1.3 kilometer. Both
cameras have a plane-parallel 12 millimeter thick anti-reflection
coated plate (ARP) in front of the CCD for radiation shielding.
The transmission curves of the focus plates, the anti-reflection
coated plates, together with the total reflectivity of the mirror
system and the quantum efficiency of the CCD are plotted in Figure
1 of Tubiana et al. 2015.
The NAC and WAC have been designed as a complementary pair that
addresses, on the one hand, the study of the nucleus surface, and,
on the other hand, the investigation of the dynamics of the
sublimation processes. The NAC, with its high spatial resolution,
was used to detect the nucleus of 67P/Churyumov-Gerasimenko from a
distance of millions of kilometers, and it is now used to study
the morphology and mineralogy of the surface and details of the
dust ejection process. The WAC has a lower spatial resolution and,
accordingly, a much wider field of view. This allows observations
of the 3D flow-field of dust and gas even if the spacecraft is near
the nucleus and provides a synoptic view of the nucleus for
context of the NAC and other instruments onboard Rosetta. To
summarize, the WAC provides long-term monitoring of the entire
nucleus and its surrounding, while the NAC studies the surface
details.
"
END_OBJECT = INSTRUMENT_INFORMATION
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "KELLERETAL2006"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
END_OBJECT = INSTRUMENT
END