Sergio Chueca

Analysis of the preliminary optical links between ARTEMIS and the Optical Ground Station

In the frame of the SILEX project, the European Space Agency (ESA) has put into orbit two Laser Communication Terminals, to establish an experimental free space optical communication link between a GEO satellite (ARTEMIS) and a LEO satellite (SPOT IV), to relay earth observation data. In order to perform In Orbit Testing (IOT) of these, and other, optical communications systems, ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreement for building the Optical Ground Station (OGS), in the Teide Observatory of the IAC. With ARTEMIS placed in a circular parking orbit at about 31000 kilometres, its optical payload has been preliminary tested with the OGS. First results and analysis are presented on the space-to-ground bi-directional link, including pointing acquisition and tracking performance, Bit-Error Rate (BER) and transmitted beam divergence effects related with atmospheric models and predictions. Future plans include deeper optical bi-directional communication tests of OGS, not only with ARTEMIS but also with OSCAR-40 (downlink) and SMART-1 (up-link) satellites, in order to do a full characterisation of the performances of laser beam propagation through atmospheric turbulence and a comparison with theoretical predictions.

JPCAM: A 1.2 GPIXEL CAMERA FOR THE J-PAS SURVEY

JPCam is a 14-CCD mosaic camera, using the new e2v 9k-by-9k 10microm-pixel 16-channel detectors, to be deployed on a dedicated 2.55m wide-field telescope at the OAJ (Observatorio Astrofisico de Javalambre) in Aragon, Spain. The camera is designed to perform a Baryon Acoustic Oscillations (BAO) survey of the northern sky. The J-PAS survey strategy will use 54 relatively narrow-band (~13.8nm) filters equi-spaced between 370 and 920nm plus 3 broad-band filters to achieve unprecedented photometric red-shift accuracies for faint galaxies over ~8000 square degrees of sky. The cryostat, detector mosaic and read electronics is being supplied by e2v under contract to J-PAS while the mechanical structure, housing the shutter and filter assembly, is being designed and constructed by a Brazilian consortium led by INPE (Instituto Nacional de Pesquisas Espaciais). Four sets of 14 filters are placed in the ambient environment, just above the dewar window but directly in line with the detectors, leading to a mosaic having ~10mm gaps between each CCD. The massive 500mm aperture shutter is expected to be supplied by the Argelander-Institut fur Astronomie, Bonn. We will present an overview of JPCam, from the filter configuration through to the CCD mosaic camera. A brief outline of the main J-PAS science projects will be included.

Ground to space optical communication characterization

Since the European Space Agency (ESA) geostationary data-relay satellite ARTEMIS started its operation in February 2003, ESA and the Instituto de Astrofisica de Canarias (IAC) have carried out routinely bidirectional optical link experiments between ARTEMIS and the Optical Ground Station (OGS), installed in the Teide Observatory of the IAC in the Canary Islands, Spain. The experiments aimed at characterizing statically and dynamically the performance of the optical downlinks and uplinks in different atmospheric turbulence conditions, together with the development and testing of appropriate theoretical models to predict the link performance. An overview of the OGS and additional facilities on top the IAC Teide Observatory is given, as well as a summary of the statistical results on propagation and communication for different experimental configurations, including different number of transmitting subapertures and divergence in the uplink. Key parameters, like scintillation and fade and surge statistics, are correlated with theoretical predictions and an analysis of the far field pattern is included. The results of the deep space uplink experiments between the OGS and ESA satellite SMART-1 are also presented. Finally ESA free space optical communication programs are summarised, including optical payloads on board different satellites.

Statistics of atmospheric parameters for multiconjugated adaptive optics for the Observatorio del Roque del los Muchachos

We present the statistical results of the optical-turbulence profiles at the Observatorio del Roque de los Muchachos over a period of six consecutive months. The data were obtained using the generalized SCIDAR technique at the 1m Jacobous Kaptein Telescope. In general, most of the turbulence is concentrated close to the observatory level (2400 m above sea level) with no more than two turbulent layers at higher altitudes. The temporal evolution along six consecutive months indicates that the turbulence is concentrated at lower altitude layers during winter. Large isoplanatic angles are also reached in winter compared to the values in spring. For the turbulence profiles measured in February, March and April we have analized the statistical position of demorfable mirrors in an ideal Multi-Conjugate Adaptive Optics system (with two or three deformable mirrors) and the improvements in the isoplanatic angles.

Propagation statistics of ground-satellite optical links with different turbulence conditions

The European Space Agency (ESA) geostationary data-relay satellite ARTEMIS started its operation in February 2003, after reaching its final position in the geostationary orbit. Since then, ESA and the Instituto de Astrofísica de Canarias (IAC) have carried out routinely bidirectional optical link experiments between ARTEMIS and the Optical Ground Station (OGS), installed in the Teide Observatory of the IAC in the Canary Islands, Spain. The main purpose of such experimental campaigns is to characterise and model the optical links performance from the propagation and communication points of view, under different atmospheric turbulence conditions. The statistical results presented in this paper cover the uplink and downlink performance, including scintillation, fade and surge statistics, intensity distributions and spectral analysis. The effect of using different number of transmitted beams and different divergences is also considered. Additionally, the results are correlated with the atmospheric turbulence conditions, in terms of profiles of the index of refraction structure constant, isoplanatic angle, seeing and wind profiles, measured in most of the cases simultaneously with the laser communication experiments

Cute SCIDAR: presentation of the new Canarian instrument and first observational results

We present a new generation SCIDAR instrument that is a fully automatically controlled device with a user-friendly interface. Alignment and observation are reduced to easy and rapid handling without the effort operating in the dome. This instrument is installed in the Jacobus Kapteyn Telescope on La Palma. We describe our progress from prototype to second generation instrument, emphasizing the design and the software for Cute SCIDAR, and show profiles from systematic monitoring using the prototype instrument on Tenerife and Cute SCIDAR on La Palma.

Ground-to-satellite bidirectional laser links for validation of atmospheric turbulence model

The European Space Agency (ESA) has launched the geostationary data-relay satellite ARTEMIS with one of its payloads being a laser communication terminal (LCT). The LCT is used within the semiconductor-laser intersatellite link experiment (SILEX) to receive Earth observation data transmitted from a similar LCT onboard the SPOT-4 satellite. To support SILEX, ESA has also reached an agreement with the Instituto de Astrofisica de Canarias (JAC) to build the Optical Ground Station (OGS), in the Teide Observatory ofthe IAC. ARTEMIS and the OGS are an ideal and unique test-bed to study and characterise laser beam propagation through atmospheric turbulence. Theoretical models of laser beam propagation through atmospheric turbulence have been reviewed and developed, to predict the performance of the optical links from the propagation and communication point of view. Special effort has been invested in modelling the uplink effects. Optical link experiments have been planned in detail, to gather the necessary data required to be statistically representative, to compare the results with theoretical predictions and to validate and adjust the theoretical models. This comparison will pave the way towards the implementation of deep-space laser communication links. The first results ofthese experiments, presenting the theoretical models, analysing separately downlink and uplink measurements, and comparing the data with the theoretical predictions, are presented.

DIPSI: measure of the tip-tilt with a diffraction image phase sensing instrument

Large segmented mirrors require efficient co-phasing techniques in order to avoid the image degradation due to segments misalignment. DIPSI (Diffraction Image Phase Sensing Instrument) is an instrument developed by IAC, GRANTECAN and LAM. This instrument is being integrated in the Active Phasing Experiment (APE), aimed at testing different phasing techniques for an Extremely Large Telescope. This paper describes the mathematical solution for determining piston and tip-tilt simultaneously from the DIPSI images. A complete set of simulations is included to study the residual errors. Residual errors are bigger when piston and tip-tilt are combined (three degrees of freedom).

Turbulence profiles in the observatories of the Canary Islands: preliminary statistics for adaptive optics

Knowledge of vertical structure of the turbulence in a site is an essential input for the requirements, performances and operation of Adaptive Optics systems. The statistics of the turbulence intensity and the coherence time of the layers affect the complexity of the design and implementation of a particular MCAO system. On the other hand, the operation of such systems could be optimized if the height and velocity of the layers were available in real time. We present statistical results of the SCIDAR turbulence profiles obtained at the observatories Canary Islands. Statistics of characteristic parameters, of special interest for MCAO, are presented here, together with their temporal evolution. The results have been checked with simultaneous meteorological measurements. We have used the balloon sounding meteorological database of the Instituto Nacional de Meteorologia of the Santa Cruz station (Tenerife) to evaluate the physical conditions related with the behavior of the optical propagation. We have compared this study with the database of indirect measurements from satellites. The reliability of these data has been proved in relation to the balloon meteorological database for all height levels on Tenerife.

The Observatorio Astrofísico de Javalambre: current status, developments, operations and strategies

The Observatorio Astrofísico de Javalambre (OAJ) is a new Spanish astronomical facility particularly designed for carrying out large sky surveys. The OAJ is mainly motivated by the development of J-PAS, the Javalambre- PAU Astrophysical Survey, an unprecedented astronomical survey that aims to observe 8500 deg2 of the sky with a set of 54 optical contiguous narrow-band filters (FWHM ~14 nm) and 5 mid and broad-band ones. J-PAS will provide a low resolution spectrum (R ~ 50) for every pixel of the Northern sky down to AB~22:5 - 23:5 per square arcsecond (at 5 σ level), depending on the narrow-band filter, and ~ 2 magnitudes deeper for the redder broad-band filters. The main telescope at the OAJ is the Javalambre Survey Telescope (JST/T250), an innovative Ritchey-Chrétien, alt-azimuthal, large-etendue telescope with a primary mirror diameter of 2.55m and 3 deg (diameter) FoV. The JST/T250 is the telescope devoted to conduct J-PAS with JPCam, a panoramic camera of 4.7 deg2 FoV and a mosaic of 14 large format CCDs that, overall, amounts to 1.2 Gpix. The second largest telescope at the OAJ is the Javalambre Auxiliary Survey Telescope (JAST/T80), a Ritchey-Chrétien, German-equatorial telescope of 82 cm primary mirror and 2 deg FoV, whose main goal is to perform J-PLUS, the Javalambre Photometric Local Universe Survey. J-PLUS will cover the same sky area of J-PAS using the panoramic camera T80Cam with 12 filters in the optical range, which are specifically defined to perform the photometric calibration of J-PAS. The OAJ project officially started in mid 2010. Four years later, the OAJ is mostly completed and the first OAJ operations have already started. The civil work and engineering installations are finished, including the telescope buildings and the domes. JAST/T80 is at the OAJ undertaking commissioning tasks, and JST/T250 is in AIV phase at the OAJ. Related astronomical subsystems like the seeing and atmospheric extinction monitors and the all-sky camera are fully operative. This paper aims to present a brief description and status of the OAJ main installations, telescopes and cameras. The current development and operation plan of the OAJ in terms of staffing organization, resources, observation scheduling, and data archiving, is also described.