1,721,130 research outputs found
Ghost images determination for the Stereoscopic Imaging Channel of SIMBIOSYS for the BepiColombo ESA mission
No full textThe Narrow Angle Camera of the MPCS suite for the MarcoPolo ESA mission: requirements and optical design solutions
No full textPossible optical designs of a Narrow Angle Camera (NAC) suitable for being the high resolution channel of the
MarcoPolo Camera System for the MarcoPolo ESA mission are presented. The MarcoPolo mission objective is the
rendezvous with a Near Earth Asteroid in order to fully characterize the body, to land on the surface and to return to
Earth a sample of the asteroid soil. Science goals for the NAC are global mapping of the object, detailed investigations of
the surface at high spatial resolution (order of millimeters), and deep examination of possible landing sites from a close
distance.
The instrument has a 3”/pixel scale factor, corresponding to 80 mm/px at 5 km from the surface, on a 1.75° × 1.75° FoV;
imaging in 5 to 8 different spectral bands (panchromatic and broadband), in the range between 400 and 900 nm, is
foreseen. Since the target is an extended low contrast object, to avoid image contrast degradation, only off-axis
unobstructed optical layouts have been considered. Solutions with two mirrors plus a refractive corrector, or allreflective
three mirrors ones, have been studied, both allowing to reach good aberration balancing over all the field of
view: the diffraction Ensquared Energy inside one pixel of the detector is of the order of 70%. To cope with the
hazardous radiation environment in which the spacecraft will be immersed in during the mission, all the glasses selected
for the design are rad-hard typ
Optical design performance of the Stereo Channel for SIMBIOSYS onboard the BepiColombo ESA mission
No full textIn this paper the adopted optical design solution for the Stereo Channel of the imaging system SIMBIOSYS
for the BepiColombo ESA mission to Mercury is presented.
The optical design of the camera together with its performance, expressed in terms of optical quality,
tolerance and stray-light analysis, are fully described.
The main scientific camera objective is the tridimensional global mapping of the entire surface of Mercury
with a scale factor of 50 m per pixel at periherm. Five different spectral bands are foreseen, a panchromatic and
four intermediate bands, in the range between 410 and 930 nm.
The Stereo Channel consists of two sub-channels looking at ±20° from nadir direction, which share the
detector and most of the optical components. The field of view of each channel is 4.8° × 5.3° with a scale factor
of 22"/pixel.
The chosen modified Schmidt configuration guarantees an optimal aberration balancing over all the field of
view and all the wavelength range; in addition the technical solution chosen for the filter manufacturing, i.e.
single substrate with stripe-butted filters, allows to further optimize chromatic aberration.
For stray-light suppression, an efficient baffling system, able to well separate the two optical paths over the
common optical elements, has been designed and an appropriate ‘filter masking’ has been foreseen to cope with
ghosts and cross talk between adjacent filter stripes.
The tolerance analysis shows that manufacturing, alignment and stability tolerances are rather relaxed. Thus
concluding, the analysis of the global optical performance of the camera assures that the scientific requirements
are optimally fulfilled
A novel optical design for planetary surface stereo-imaging: preliminary design of the stereoscopic imaging channel of SIMBIOSYS for the BepiColombo ESA mission
No full textThe optical design of the STereoscopic imaging Channel (STC) of the imaging/spectroscopic system SIMBIOSYS for
the ESA BepiColombo mission is presented. The main aim of this system is the global stereo mapping of planet
Mercury surface during the BepiColombo mission lifetime.
The instrument consists of two identical cameras looking at ±20° from nadir which are sharing some optical
components and the detector. The instrument has a 23”/pixel scale factor, corresponding to 50 m/px at 400 km from the
surface, on a 4° × 4° FoV; imaging in four different spectral bands, between 540 nm and 890 nm, is foreseen. The STC
optical characteristics guarantee global stereo mapping of the whole Mercury surface with all the filters.
The coupling of an achromatic air-spaced doublet with a relay lens system allows good aberration balancing over
all the field of view: the diffraction Ensquared Energy inside one pixel of the detector is of the order of 80%. In
addition, an intermediate field stop gives the possibility of designing an efficient baffling system for straylight rejection.
To cope with the hazardous radiation environment in which the spacecraft will be immersed in during the mission,
all the glasses selected for the design are rad-hard type.
A preliminary tolerance analysis has also been undertaken showing a low criticality level for manufacturing,
alignment and stability of the system
Preliminary error budget analysis of the coronagraphic instrument METIS for the Solar Orbiter ESA mission
No full textSpectroscopy, is the solar coronagraph foreseen for the ESA
Solar Orbiter mission. METIS is conceived to image the solar
corona from a near-Sun orbit in three different spectral bands: in
the HeII EUV narrow band at 30.4 nm, in the HI UV narrow
band at 121.6 nm, and in the polarized visible light band (590 –
650 nm). It also incorporates the capability of multi-slit
spectroscopy of the corona in the UV/EUV range at different
heliocentric heights.
METIS is an externally occulted coronagraph which adopts an
“inverted occulted” configuration. The Inverted external occulter
(IEO) is a small circular aperture at the METIS entrance; the
Sun-disk light is rejected by a spherical mirror M0 through the
same aperture, while the coronal light is collected by two annular
mirrors M1-M2 realizing a Gregorian telescope. To allocate the
spectroscopic part, one portion of the M2 is covered by a grating
(i.e. approximately 1/8 of the solar corona will not be imaged).
This paper presents the error budget analysis for this newconcept
coronagraph configuration, which incorporates 3
different sub-channels: UV and EUV imaging sub-channel, in
which the UV and EUV light paths have in common the detector
and all of the optical elements but a filter, the polarimetric visible
light sub-channel which, after the telescope optics, has a
dedicated relay optics and a polarizing unit, and the
spectroscopic sub-channel, which shares the filters and the
detector with the UV-EUV imaging one, but includes a grating
instead of the secondary mirror.
The tolerance analysis of such an instrument is quite complex:
in fact not only the optical performance for the 3 sub-channels
has to be maintained simultaneously, but also the positions of M0
and of the occulters (IEO, internal occulter and Lyot stop), which
guarantee the optimal disk light suppression, have to be taken
into account as tolerancing parameters.
In the aim of assuring the scientific requirements are optimally
fulfilled for all the sub-channels, the preliminary results of
manufacturing, alignment and stability tolerance analysis for the
whole instrument will be described and discussed
Analysis of tectonics and cryovolcanism on Ganymede: possible observations with JGO-EJSM
No full textVoyager data revealed that the Jovian moon
Ganymede, the biggest satellite in the solar system,
consists of ancient heavily cratered dark terrain and
younger resurfaced and tectonically deformed bright
terrain (groove lanes and polygons). These terrains
seem to have undergone an intense resurfacing and
several models were developed. However both
Voyager data and successively in 1996 Galileo SSI
(Solid State Imager) images did not have a spatial
resolution high enough to define the most likely
resurfacing phenomena. In particular Galileo data
coverage is not global (fig. 1) and there is a great
heterogeneity in the spatial resolution going from
more than 500 m/pixel in some areas to 100 m/pixel
in a very few areas. The WAC (Wide Angle Camera),
which should be on board the ESA mission JGOEJSM,
will provide a global coverage of Ganymede’s
surface with a constant spatial resolution of 150
m/pixel to perform in-depth geologic studies
METIS- ESA Solar Orbiter mission internal straylight analysis
No full textMETIS is the Multi Element Telescope for Imaging and Spectroscopy for the ESA Solar Orbiter. Its target is the
solar corona from a near-Sun orbit in two different spectral bands: the HI UV narrow band at 121.6 nm, and the
VL visible light band. METIS adopts a novel inverted externally occulted configuration, where the disk light is
shielded by an annular occulter, and an annular aspherical mirror M1 collects the signal coming from the
corona. After M1 the coronal light passes through an internal occulter and is then reflected by a second annular
mirror M2 toward a narrow filter for the 121.6 nm HI line selection. The visible light reflected by the filter is
used to feed a visible light (580 – 640 nm) polarimetric channel. The photospheric light passing through the
entrance aperture is back-rejected by a spherical rejection mirror.
Since the coronal light is enormously fainter than the photospheric one, a very tough suppression is needed for
the internal stray light, in particular the requirement for the stray light suppression is more stringent in the VL
than in the UV, because the emission of the corona with respect to the disk emission is different in the two
cases, and the requirements are a suppression of at least 10-9 times for the VL and a suppression of at least 10-7
times for the UV channel.
This paper presents the stray light analysis for this new coronographic configuration.
The complexity of the optomechanical design of METIS, combined with the faintness of the coronal light with
respect to the solar disk noise, make a standard ray tracing approach not feasible because it is not sufficient to
stop at the first generation of scattered rays in order to check the requirements. Also scattered rays down to the
fourth generation must be treated as sources of new scattering light, to analyze the required level of accuracy. If
used in a standard ray tracing scattering analysis, this approach is absolutely beyond the computational
capabilities today available; therefore we opted for a scattering ray generation with a Montecarlo method in
which after a father ray hits a surface, only one ray is generated, randomly selected according to the distribution
of the transmitted energy. These rays bring with them all the energy that is otherwise distributed between all the
rays of second generation, making the model more realistic and avoiding loss of energy due to the rays
sampling. The stray light has been studied in function of the mechanical roughness of the surfaces and the
obtained results indicate an instrument stray light blocking performance well within the requirements in both
channels
Calibration of the wide-angle camera for the Rosetta mission: preliminary results on the flight model
No full textA novel optical design for the stereo channel of the imaging system Simbiosys for the BepiColombo ESA mission
No full textIn this paper the design of a novel catadioptric optical
solution for the Stereo Channel (STC) of the imaging
system SIMBIOSYS for the BepiColombo ESA
mission to Mercury is presented.
The main scientific objective is the 3D global mapping
of the entire surface of Mercury with a scale factor of
50 m per pixel at periherm in five different spectral
bands.
The system consists of two sub-channels looking at
±20° from nadir. They share the detector and all the
optical components with the exception of the first
element, a rhomboid prism. The field of view of each
channel is 5.3° ́ 4.5° and the scale factor is 23
arcsec/pixel. The system guarantees an aberration
balancing over all the field of view and wavelength
range with optimal optical performance.
For stray-light suppression, an efficient baffling system
able to well decouple the optical paths of the two subchannels
has been designed
Preliminary optical design of the stereo channel of the imaging system SIMBIOSYS for the BepiColombo ESA mission
No full textThe paper describes the optical design and
performance budget of a novel catadioptric instrument
chosen as baseline for the Stereo Channel (STC) of the
imaging system SIMBIOSYS for the BepiColombo
ESA mission to Mercury.
The main scientific objective is the 3D global mapping
of the entire surface of Mercury with a scale factor of
50 m per pixel at periherm in four different spectral
bands.
The system consists of two twin cameras looking at
±20° from nadir and sharing some components, such as
the relay element in front of the detector and the
detector itself. The field of view of each channel is 4° x
4° with a scale factor of 23’’/pixel. The system
guarantees good optical performance with Ensquared
Energy of the order of 80% in one pixel.
For the straylight suppression, an intermediate field
stop is foreseen, which gives the possibility to design
an efficient baffling system
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