Abstract
The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19-20. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovae (including SNIa), search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System, and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.
1. Introduction
The MASTER project (Mobile Astronomical System of TElescope Robots) was launched in 2002, when the first Russian robotic telescope was installed near Moscow on an automated mounting with automatic roof, weather station, and alert system (Lipunov et al. [1–3]). By early 2008 we posted about 100 GCN circulars, recorded optical emission from three gamma-ray bursts, and discovered four supernovae (Lipunov et al. [4], Tyurina et al. [5]). Unfortunately, very poor astroclimatic conditions near Moscow made it impossible to demonstrate the potential of our telescope to its full extent. However, we obtained about 80 000 images, each with a size of six square degrees, and used them to successfully develop a software pipeline, which allows us not only to perform in real time the extraction of images and their astrometric and photometric reduction, but also to automatically classify the sources identified; that is, determine which type of astronomical objects (supernovae, minor planets, comets, man-made satellites, meteors, or optical transients) they belong to (Figures 1 and 2). Moreover, our facility can also be used for alert observations of optical emission of gamma-ray bursts (Tyurina et al. [5]).
Our experience with the operation of robotic telescopes allowed us to develop the wide-field MASTER optical facility with optimum parameters, which can be used to address a wide range of astrophysical tasks. We actually developed a multipurpose optical facility, which is similar in composition to the one independently proposed by Bogdan Paczynski (Paczynski [6]). The first MASTER telescopes and their individual components are already installed at three sites in Russia—near Kislovodsk (Caucasian Mountain Observatory of the Sternberg Astronomical Institute of the Moscow State University), in Urals (Kourovka Observatory of Ural State University), and near Irkutsk (Irkutsk State University Observatory). In summer 2009 we also plan to deploy similar facilities near Irkutsk and Blagoveshchensk.
2. MASTER Wide-Field Robotic Facility
The MASTER wide-field robotic telescope that we developed is manufactured by OAO Optika Moscow Association. The facility consists of two instruments: MASTER II wide-field optical telescope “Santel 400” and MASTER very wide-field (VWF) cameras.
2.1. MASTER II Wide-Field Robotic Telescope
A single fast German equatorial mounting carries two 1 : 2.5 focal-ratio symmetrical high-aperture 400-mm catadioptric telescopes (Figure 3). The telescope has an extra degree of freedom, which allows their tubes to be aligned or misaligned, making it possible to double the size of the field of view and, when operating in the alert mode (with collinear tubes), to perform synchronous photometry of rapidly varying objects in standard broad-band filters (B,V,R,I) and their polarimetry at different polarizations (Figure 4).
Table 1 lists the technical parameters of MASTER II telescope. The telescope is equipped with a shell-type automatic shelter, which, when open, allows the entire sky to be observed. This facility is also equipped with a time synchronization system, a weather station, and a cloud cover sensor.
2.2. MASTER VWF Very Wide-Field Camera
V. G. Kornilov developed a robotic very wide-field MASTER VWF camera with a maximum field of view of 1000 square degrees (Figure 5) for synchronous observations of optical emission from gamma-ray bursts. The facility uses a parallactic fork capable of carrying 2 CCD cameras with up to 10-cm aperture lenses. The facility has an autonomous high-quality roof designed by N. I. Shatskii. Our experience of its operation under extreme conditions of Russian winter (with temperatures as low as degree Celsius) demonstrates good survival potential of all systems. Table 2 lists the specifications of the very wide-field camera. The cameras are adapted to all large-aperture Nikor and Nikor-Ziess lenses. Our facility uses two lenses with the focal distances of 50 and 85 mm. The cameras allow continuous sky imaging with a minimum exposure of 150 milliseconds.
3. Geographic Location of the Stations of the MASTER Network as of May 2009
The locations of the station sites were determined by two factors: (1) sites must be about 2 hours apart in longitude and (2) sites must provide minimum required infrastructure (power supply, Internet, warm room for servers). Such sites can usually be found at university observatories (Figure 6).
The participants to the project already include Moscow State University (Figure 7), Ural State University (Figure 8), Irkutsk State University, and Blagoveshchensk Pedagogical University. The network extends over seven hours in longitude, thereby ensuring virtually continuous 24-hour observations during winter seasons.
When deployed, the first step MASTER II telescope network will have the following parameters
(i)Total field of view— square degrees.(ii)Survey rate—2000 square degrees per hour down to a limiting magnitude of 19-20.(iii)Alert positioning speed-up to 30 degrees/s.4. Expected Scientific Results
4.1. GRB Mystery
Observations of the prompt emission of gamma-ray bursts, which is determined by the physical processes in the central engine, are of fundamental importance for understanding the nature of these bursts (Lipunov and Gorbovskoy [7, 8]).
First and foremost, we expect that MASTER II telescopes will allow us to obtain multicolor photometric and polarimetric follow-up observations for alerts from gamma-ray space observatories. We also plan to continue synchronous observations with very wide-field cameras. Recall that we have performed five synchronous observations of gamma-ray error boxes since November 2008 (Gorbovskoy et al. [9]).
4.2. Dark Energy
The first mass observations of type Ia supernovae showed (Reiss et al.[10]; Perlmutter S. et al.[11]) that the Universe expands with acceleration, which may be due to the so-called dark energy. This result follows from observations of several dozen supernovae. On the other hand, present-day search surveys miss most of the supernovae. The first computations of the velocities of explosions of cosmological supernovae performed by Jorgensen et al., [12] showed that the number of supernovae exploding in our Universe with magnitudes brighter than m can be described by the following formula:
Note that without the correction for host-galaxy extinction corresponds to a redshift of , where the effect of cosmic energy of vacuum becomes quite appreciable.
This actually means that MASTER can discover several thousand supernovae annually and perform multicolor photometry of these objects.
5. Conclusion
A complete survey of the entire visible sky during a single night will allow to perform a number of tasks with no special observing plan (provided, naturally, proper coordination between the stations of the network):
(i)search for orphan flares,(ii)search for exoplanets,(iii)search for dangerous asteroids,(iv)search for microlensing effects,(v)search for and monitoring of space waste.Acknowledgment
The authors thank the General Director of the “OPTIKA” Association S. M. Bodrov for providing the MASTER project with necessary expensive equipment.