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Pi of the Sky is a system of wide field of view robotic telescopes, which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system was designed for autonomous operation, monitoring a large fraction of the sky to a depth of 12m−13m and with time resolution of the order of 10 seconds. Custom designed CCD cameras are equipped with Canon lenses f = 85 mm, f/d = 1.2 and cover 20° × 20° of the sky each. The final system with 16 cameras on 4 equatorial mounts was completed in 2014 at the INTA El Arenosillo Test Centre in Spain. GRB160625B was an extremely bright GRB with three distinct emission episodes. Cameras of the Pi of the Sky observatory in Spain were not observing the position of the GRB160625B prior to the first emission episode. Observations started only after receiving Fermi/GBM trigger, about 140 seconds prior to the second emission. As the position estimate taken from the Fermi alert and used to position the telescope was not very accurate, the actual position of the burst happened to be in the overlap region of two cameras, resulting in two independent sets of measurements. Light curves from both cameras were reconstructed using the Luiza framework. No object brighter than 12.4m (3σ limit) was observed prior to the second GRB emission. An optical flash was identified on an image starting -5.9s before the time of the Fermi/LAT trigger, brightening to about 8m on the next image and then becoming gradually dimmer, fading below our sensitivity after about 400s. Emission features as measured in different spectral bands indicate that the three emission episodes of GRB160625B were dominated by distinct physics process. Simultaneously observations in gamma-rays and optical wavelengths support the hypothesis that this was the first observed transition from thermal to non-thermal radiation in a single GRB. Main results of the combined analysis are presented.

The main goal of the “Pi of the Sky” project is search for optical transients (OTs) of astrophysical origin, in particular those related to gamma-ray bursts (GRBs). Since March 2011 the project has two running observatories: one in northern Chile and the other one in southern Spain. This allows for regular observations of a common sky fields, visible from both observatories which are scheduled usually 1–2 h per night. In such a case, the on-line flash recognition algorithm, looking for optical transients, can use parallax information to assure that events observed from both sites have parallax angle smaller than the error of astrometry. On the other hand, the remaining OT candidates can be verified against a hypothesis of being near-Earth objects. This paper presents algorithm using parallax information for identification of near-Earth objects, which might be satellites, or space debris elements. Preliminary results of the algorithm are also presented.

"Pi of the Sky" is a system of wide field of view robotic telescopes, which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system was designed for autonomous operation, monitoring a large fraction of the sky with 12m-13m range and time resolution of the order of 1 - 10 seconds. For now there are two working "Pi of the Sky" observatories: in San Pedro de Atacama (Chile) and near Mazagon in Southern Spain. In this paper we report on the status of the project, as well as recent observation of asteroid 2004BL86, which passed the Earth in late January 2015, DG CVn outburst in 2014, satellites observations and our future plans.

Pi of the Sky is a system of wide field-of-view robotic telescopes which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system is designed for autonomous operation, follows the predefined observing strategy and adopts it to the actual conditions. We describe the current status of telescopes located in Chile and Spain and prospects for future development.

Pi of the Sky is a system of wide field-of-view robotic telescopes designed for observations of short timescale astrophysical phenomena, especially for prompt optical GRB emission. The apparatus was designed for autonomous operation, follows the predefined observing strategy and adopts it to the actual conditions, monitoring a large part of the sky with time resolution of the order of 1 - 10 seconds and range 12m-13m. Observation strategy and system design was successfully tested with a prototype detector working in 2004-2009 at Las Campanas Observatory, Chile, and moved to San Pedro de Atacama Observatory in March 2011. In October 2010 the first unit of the final Pi of the Sky detector system, with 4 CCD cameras, was successfully installed in the INTA El Arenosillo Test Centre in Spain. Simultaneous observations from locations in Chile and Spain allow a systematic search for optical transients of cosmological origin. Accurate analysis of data arising from a wide-field system like Pi of the Sky is a real challenge because of a number of factors that can influence the measurements. We have developed a set of dedicated algorithms which remove poor quality measurements, improve photometric accuracy and allow us to reach uncertainties as low as 0.015– 0.02 mag. Three more units (12 CCD cameras) are being prepared for installation on a new platform in INTA, aiming at a total coverage of about 6400 square degrees. Status and performance of the detectors is presented.

One of the possible approaches to detecting optical counterparts of GRBs requires monitoring large parts of the sky. This idea has gained some instrumental support in recent years, such as with the "Pi of the Sky" project. The broad sky coverage of the "Pi of the Sky" apparatus results from using cameras with wide-angle lenses (20x20 deg field of view). Optics of this kind introduce significant deformations of the point spread function (PSF), increasing with the distance from the frame centre. A deformed PSF results in additional uncertainties in data analysis. Our aim was to create a model describing highly deformed PSF in optical astronomy, allowing uncertainties caused by image deformations to be reduced. Detailed laboratory measurements of PSF, pixel sensitivity, and pixel response functions were performed. These data were used to create an effective high quality polynomial model of the PSF. Finally, tuning the model and tests in applications to the real sky data were performed. We have developed a PSF model that accurately describes even very deformed stars in our wide-field experiment. The model is suitable for use in any other experiment with similar image deformation, with a simple tuning of its parameters. Applying this model to astrometric procedures results in a significant improvement over standard methods, while basic photometry precision performed with the model is comparable to the results of an optimised aperture algorithm. Additionally, the model was used to search for a weak signal -- namely a possible gamma ray burst optical precursor -- showing very promising results. Precise modelling of the PSF function significantly improves the astrometric precision and enhances the discovery potential of a wide-field system with lens optics., Accepted for publication in Astronomy and Astrophysics on 13 December 2012

Starting March 2011 the “Pi of the Sky” project has two observatories in use: in northern Chile and in southern Spain. Since then we are able to observe a parallax of objects, which pass close to the Earth. Simultaneous observations from two sites are very important to us, because this allows us to reject false flash observations, due to cosmic radiation, meteors, planes, etc. In this paper we present theoretical limitations of our parallax observations. Moreover, first results are shown.

Pi of the Sky is a system of wide field-of-view robotic telescopes which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system is designed for autonomous operation, follows the predefined observing strategy and adopts it to the actual conditions. Simultaneous observations from locations in Chile and Spain allow a systematic search for optical transients of cosmological origin. Accurate analysis of data arising from a wide-field system like Pi of the Sky is a real challenge because of a number of factors that can influence the measurements. We have developed a set of dedicated algorithms which remove poor quality measurements, improve photometric accuracy and allow us to reach uncertainties as low as 0.015‐ 0.02 mag.

In October 2010 Pi of the Sky set up a new system, consisting of 4 cameras installed on a new mount, in El Arenosillo, in southern Spain. It was followed by moving the prototype system from Las Campanas Observatory (central Chile) to San Pedro de Atacama (northern Chile) in March 2011. In this paper our new sites, some details about observational conditions and first results in both observatories are described.

Pi of the Sky is a system of robotic telescopes designed for observations of short timescale astrophysical phenomena, e.g. prompt optical GRB emissions. The apparatus is designed to monitor a large fraction of the sky with 12–13 m range and time resolution of the order of 1–10 seconds. In October 2010 the first unit of the new Pi of the Sky detector system was successfully installed in the INTA El Arenosillo Test Centre in Spain. We also moved our prototype detector from Las Campanas Observatory to San Pedro de Atacama Observatory in March 2011. The status and performance of both detectors is presented.

Modern research trends require observation of fainter and fainter astronomical objects on large areas of the sky. This implies usage of systems with high temporal and optical resolution with computer based data acquisition and processing. Therefore Charge Coupled Devices (CCD) became so popular. They offer quick picture conversion with much better quality than film based technologies. This work is theoretical and practical study of the CCD based picture acquisition system. The system was optimized for "Pi of The Sky" project. But it can be adapted to another professional astronomical researches. The work includes issue of picture conversion, signal acquisition, data transfer and mechanical construction of the device.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

"Pi of the Sky" is a detector designed for search for optical flashes of the cosmic origin in the sky. Its primary goal is to look for optical afterglows associated with the gamma ray bursts (GRB), but it is also good to tool to study any kind of short timescale astrophysical phenomena. The apparatus consists of two arrays of 16 cameras each, which allow for simultaneous observation of big fraction of the sky. Due to on-line data analysis in the real time, it has self-triggering capability and can react to external triggers with negative time delay. The prototype with two cameras has been installed at Las Campanas (Chile) and was operational in period since June 2004 till August 2005 and upgraded in June 2006. Database for storing large amount of astronomical measurements was developed. The general idea of experiment, apparatus and data analysis in the experiment will be presented.

"Pi of the Sky" is a detector designed for search for optical flashes of cosmic origin in the sky. Its primary goal is to look for optical afterglows associated with the gamma ray bursts (GRB) but it is capable to detect also other optical transients of extragalactic origin. The apparatus consists of two arrays of 16 cameras each, which allow for simultaneous observation of large part of the sky. Thanks to on-line data analysis in real time, it has self-triggering capability and can react to external triggers with negative time delay. The prototype with two cameras has been installed at Las Campanas (Chile) and is operational from July 2004. General idea of experiment, the apparatus and its performance will be presented.

Modem research trends require observation of fainter and fainter astronomical objects on large areas of the sky. This implies usage of systems with high temporal and optical resolution with computer based data acquisition and processing. Therefore Charge Coupled Devices became so popular. They offer quick picture conversion with much better quality than film based technologies. This work is theoretical and practical study of the CCD based picture acquisition system. The system was optimized for "Pi of The Sky" project. But it can be adapted to another professional astronomical researches. The work includes issue of picture conversion, signal acquisition, data transfer and mechanical construction of the device.

"Pi of the Sky" is a detector designed for search for optical flashes of the cosmic origin in the sky. Its primary goal is to look for optical afterglows associated with the gamma ray bursts (GRB), but it is capable to detect also other optical transients of extragalactic origin. The apparatus consists of two arrays of 16 cameras each, which allow for simultaneous observation of the whole sky. Due to on-line data analysis in the real time, it has self-triggering capability and can react to external triggers with negative time delay. The prototype with two cameras has been installed at Las Campanas (Chile) and is operational from July 2004. General idea of experiment, the apparatus and its performance will be presented. Physical results will be reviewed and perspectives for the future will be outlined.

An apparatus to search for optical flashes in the sky is described. It has been optimized for optical counterparts of gamma ray bursts (GRB). It consists of 2 × 16 cameras covering all the sky. The sky is monitored continuously and the data are analyzed on-line. The apparatus has self-triggering capability and can react to external triggers with negative delay. The prototype with two cameras has been installed at Las Campanas (Chile) and is operational from July 2004. The paper presents the general idea of the experiment and describes the apparatus in detail. The performance of the prototype is briefly reviewed and perspectives for the future are outlined.

Institute of Electronic Systems, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warsaw, Poland Institute of Experimental Physics, Faculty of Physics, Warsaw University, Hoza 69, 00-681 Warsaw, Poland Center for Theoretical Physics PAN, Al. Lotnikow 32/46, 00-668 Warsaw, Poland Astronomical Observatory, Warsaw University, Al. Ujazdowskie 4, 00-478 Warsaw, Poland Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw, Poland

An apparatus is described to search for optical, point-like flashes in the sky at the time scale of seconds. Such flashes are expected to accompany gamma ray bursts (GRB) observed routinely by satellites and proven to be of extragalactic origin. So far only one such flash has been recorded shortly after the GRB, because standard methods of observational astronomy are not suitable for the time scale of seconds. In this paper, a novel approach is proposed based on experience from particle physics experiments. An apparatus is described which monitors the sky continuously. The large data stream is analysed on-line and potentially interesting events are selected by a multilevel trigger system. In the first phase of the project the apparatus consists of two CCD cameras, especially designed for this project and a robotic mount used to scan interesting regions of the sky. In the second phase the experiment will consist of two sets of 16 cameras on fixed mounts, covering almost all visible sky.