This paper presents the recent achievements in the development of ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), a solar coronagraph that is the primary payload of ESA’s formation flying in-orbit demonstration mission PROBA-3. The PROBA-3 Coronagraph System is designed as a classical externally occulted Lyot coronagraph but it takes advantage of the opportunity to place the 1.4 meter wide external occulter on a companion spacecraft, about 150m apart, to perform high resolution imaging of the inner corona of the Sun as close as ~1.1 solar radii. Besides providing scientific data, ASPIICS is also equipped with sensors for providing relevant navigation data to the Formation Flying GNC system. This paper is reviewing the recent development status of the ASPIICS instrument as it passed CDR, following detailed design of all the sub-systems and testing of STM and various Breadboard models.
Proc. SPIE. 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave
KEYWORDS: Telescopes, Metrology, Metrology, Surface plasmons, Light emitting diodes, Calibration, Satellites, Coronagraphy, Space telescopes, Space telescopes, Space operations, Space operations, Solar processes
Formation flying is one of the most promising techniques for the future of astronomy and astrophysics from the space.
The capabilities of the rockets strongly affect the dimensions and the weights of telescopes and instrumentation to be
launched. Telescopes composed by several smallest satellites in formation flying, could be the key for build big space
telescopes. With this aim, the ESA PROBA-3 mission will demonstrate the capabilities of this technology, maintaining
two satellites aligned within 1 mm (longitudinal) when the nominal distance between the two is of around 144m.
The scientific objective of the mission is the observation of the solar corona down to 1.08 solar radii. The Coronagraph
Spacecraft (CSC) will observe the Sun, when the second spacecraft, the Occulter Spacecraft (OSC) will work as an
external occulter, eclipsing to the CSC the sun disk. The finest metrology sub-systems, the Shadow Position Sensors
(SPS) and the Occulter Position Sensor Emitters (OPSE) identifying respectively the CSC-Sun axis and the formation
flying (i.e., CSC-OSC) axis will be considered here. In particular, this paper is dedicated to the test-bed for the
characterization, the performance analysis and the algorithms capabilities analysis of the both the metrology subsystems.
The test-bed is able to simulate the different flight conditions of the two spacecraft and will give the opportunity to check
the response of the subsystems in the conditions as close as possible to the flight ones.
years have raised increasing interest. Many applications of astronomical observation techniques, as coronography and
interferometry get great benefit when moved in space and the employment of diluted systems represents a milestone to
step-over in astronomical research. In this work, we present the Optical Position Sensors Emitter (OPSE) metrological
sub-system on-board of the PROBA3. PROBA3 is an ESA technology mission that will test in-orbit many metrology
techniques for the maintenance of a Formation Flying with two satellites, in this case an occulter and a main satellite
housing a coronagraph named ASPIICS, kept at an average inter-distance of 144m. The scientific task is the observation
of the Sun’s Corona at high spatial and temporal resolution down to 1.08R⊙. The OPSE will monitor the relative position
of the two satellites and consists of 3 emitters positioned on the rear surface of the occulter, that will be observed by the
coronagraph itself. A Centre of Gravity (CoG) algorithm is used to monitor the emitter’s PSF at the focal plane of the
Coronagraph retrieving the Occulter position with respect to the main spacecraft. The 3σ location target accuracy is
300μm for lateral movement and 21cm for longitudinal movements. A description of the characterization tests on the
OPSE LED sources, and of the design for a laboratory set-up for on ground testing is given with a preliminary
assessment of the performances expected from the OPSE images centroiding algorithm.
In recent years, ESA has assessed several mission involving formation flying (FF). The great interest in this topics is mainly driven by the need for moving from ground to space the location of next generation astronomical telescopes overcoming most of the critical problems, as example the construction of huge baselines for interferometry. In this scenario, metrology systems play a critical role. PROBA3 is an ESA technology mission devoted to in-orbit demonstration of the FF technique, with two satellites, an occulter and a main satellite housing a coronagraph named ASPIICS, kept at an average inter-distance by about 144m, with micron scale accuracy. The guiding proposal is to test several metrology solution for spacecraft alignment, with the important scientific return of having observation of Corona at never reached before angular field. The Shadow Position Sensors (SPS), and the Optical Position Emitters Sensors (OPSE) are two of the systems used for FF fine tracking. The SPS are finalized to monitor the position of the two spacecraft with respect to the Sun and are discussed in dedicated papers presented in this conference. The OPSE will monitor the relative position of the two satellites and consists of 3 emitters positioned on the rear surface of the occulter, that will be observed by the coronagraph itself. By following the evolution of the emitters images at the focal plane the alignment of the two spacecrafts is retrieved via dedicated centroiding algoritm. We present an overview of the OPSE system and of the centroiding approach.
The aim of the present work is to prepare, test and analyze the electrical and optical characteristics of the p-
NiO/n-Si and n-ZnO/p-Si heterojunctions as building blocks in semiconductor devices. p-NiO thin films of 75 nm have
been prepared by thermal oxidation of Ni metallic films of 50 nm deposited by e-beam high vacuum evaporation
technique on n type silicon wafer with 30 Ω cm resistivity. The oxidation processes of nickel samples are performed at
430oC for 60 min in a controlled ambient of oxygen and argon maintaining the oxygen concentration of 70%. The structural characteristics observed by X - ray diffraction method showed a polycrystalline structure with strong peaks corresponding to cubic NiO. p-NiO / (n/n+) Si heterojunctions I-V characteristics revealed that p-type NiO thin films have been obtained and a value of ~2.2 V for forward threshold voltage. n-ZnO thin layers of about 200 nm thickness, doped with aluminum on 30 Ωcm resistivity p type silicon epitaxial wafers were obtained by spin coating, layer by layer, using zinc acetate (Zn(CH3COO)2⋅2H2O) and aluminum nitrate (Al(NO3)3⋅9H2O) with Al/ Al+Zn ratio in range 0.5 - 1.5 % followed by thermal treatment at 475 °C for 15 minutes. The obtained thin layers have a high transparency T>85% for NiO and >70 % for ZnO:Al) over a large spectral range and a low resistivity, ρ~10-4 Ωcm. The I-V characteristics of p-NiO/n– Si shows that this heterojunction has rectifying properties with turn on voltage in the range 1.5- 2V and reverse breakdown voltage >10 V. By fitting the forward voltage we have obtained for p-NiO/n-Si a series resistance id RS=16 kΩ, an ideality factor of >10 and a barrier height of 0.648 eV. The optical response of n-ZnO/p- Si heterojunction was investigated at λp = 475 nm and the measured values of the photocurrent about 10 μA confirms the possibility to use them as ultraviolet radiation detectors.
In this paper the results of the simulation for a bimorph actuated micromirror on silicon substrate are presented. The
response of the micromirrors, consisting in the displacement along z axis was investigated in static and dynamic regimes
using Coventor software taking into account the material parameters and geometry of the structure. The structure is made from
two layers gold and silicon oxide. The gold layer of the structure is patterned in two parts, one actuating part and one
reflecting part. Due to this patterning thermal conduction through the gold layer is interrupted and as a result the reflective
surface curling is reduced, thus improving reflectivity. The simulations were carried out in order to obtain an optimized
structure geometry. We optimized the actuating part geometry analyzing convection, radiation, von Misses stress, temperature
and displacement. As a result we need an actuating part with almost constant temperature and von Misses stress and higher
displacement. Also we made simulations in order to reduce the stress in the reflective surface.
This paper reports fabrication methods of polymer-based micro/nano optical structures based on replica molding.
Various molds have been used: polymer, silicon, and SiO2-based. Different types of treatment and release agent were
investigated in order to achieve an optimum demolding. Diffractive optical elements, micro-lenses and antireflective
layers have been obtained in commercial or doped polymers with controlled refractive index. The quality of the
replication was investigated using optical microscopy, SEM, profilometry and functional tests. The micro-optical
components can be transferred onto silicon silicon chip with photodetectors, or photonic integrated circuits using
We report an analytical model for calculation of reflection and transmission coefficients of a Bragg reflector with periodic structure using transfer matrix method. Using explicit expressions for these coefficients, the reflectivity of the periodic structures for different pairs of layers and layer thickness was simulated. We investigate the reflectivity of the periodic structures consisting of following pairs of successive layers: SiO2 /Si3N4 (low ratio of refractive indexes); poly-Si/ SiO2 (high ratio), Si/air-gap (high contrast). The theoretical and experimental investigations of a particular periodic structure consisting of SiO2/Au are also presented. Our method allows the rapid evaluation of reflectance of Bragg reflector with periodic structure.