The Astro-WISE approach to quality control for astronomical data

We present a novel approach to quality control during the processing of astronomical data. Quality control in the Astro-WISE Information System is integral to all aspects of data handing and provides transparent access to quality estimators for all stages of data reduction from the raw image to the final catalog. The implementation of quality control mechanisms relies on the core features in this Astro-WISE Environment (AWE): an object-oriented framework, full data lineage, and both forward and backward chaining. Quality control information can be accessed via the command-line awe-prompt and the web-based Quality-WISE service. The quality control system is described and qualified using archive data from the 8-CCD Wide Field Imager (WFI) instrument (http://www.eso.org/lasilla/instruments/wfi/) on the 2.2-m MPG/ESO telescope at La Silla and (pre-)survey data from the 32-CCD OmegaCAM instrument (http://www.astro-wise.org/~omegacam/) on the VST telescope at Paranal.     

A new Bolivia-USSR astronomical observatory and its astrometric activities

In 1982 a Bolivia-USSR astronomical observatory began its activities near Tarija, Bolivia. Observations of 200 000 faint stars, 2822 bright stars (m6) and Halley's comet have been made with the expedition's astrograph.     

NBFTP: a dedicated data transfer system for remote astronomical observation at Dome A

Dome A,Antarctica,has been thought to be one of the best astronomical sites on the Earth for decades.Since it was first visited by astronomers in 2008,dozens of facilities for astronomical observation and site testing were deployed.Due to its special geographical location,the data and message exchange between Dome A and the domestic control center could only depend on Iridium.Because the link bandwidth of Iridium is extremely limited,the network traffic cost is quite expensive and the network is rather unstable,the commonly used data transfer tools,such as rsync and scp,are not suitable in this case.In this paper,we design and implement a data transfer tool called NBFTP(narrow bandwidth file transfer protocol)for the astronomical observation of Dome A.NBFTP uses a uniform interface to arrange all types of data and matches specific transmission schemes for different data types according to rules.Break-point resuming and extensibility functions are also implemented.Our experimental results show that NBFTP consumes 60%less network traffic than rsync when detecting the data pending to be transferred.When transferring small files of 1 KB,the network traffic consumption of NBFTP is 40%less than rsync.However,as the file size increases,the network traffic consumption of NBFTP tends to approach rsync,but it is still smaller than rsync.     

Antenna data storage concept for phased array radio astronomical instruments

Low frequency Radio Astronomy instruments like LOFAR and SKA-LOW use arrays of dipole antennas for the collection of radio signals from the sky. Due to the large number of antennas involved, the total data rate produced by all the antennas is enormous. Storage of the antenna data is both economically and technologically infeasible using the current state of the art storage technology. Therefore, real-time processing of the antenna voltage data using beam forming and correlation is applied to achieve a data reduction throughout the signal chain. However, most science could equally well be performed using an archive of raw antenna voltage data coming straight from the A/D converters instead of capturing and processing the antenna data in real time over and over again. Trends on storage and computing technology make such an approach feasible on a time scale of approximately 10 years. The benefits of such a system approach are more science output and a higher flexibility with respect to the science operations. In this paper we present a radically new system concept for a radio telescope based on storage of raw antenna data. LOFAR is used as an example for such a future instrument.     

Some new astronomical facilities in China

For the 1990's, plans for some astronomical facilities and related researchers are being carried out in China. In this report we describe in some details the plans of radio astronomical facilities, 150/220 cm Schmidt telescope, and experiments on porcelain mirror material.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

A new spectrum analyzer for radio astronomical studies with the radio telescope RATAN-600

The spectral measuring facility with a new Fourier analyzer for use with the radio telescope RATAN-600 is described and its experimental data are reported.     

Enhanced management of personal astronomical data with FITSManager

Although the roles of data centers and computing centers are becoming more and more important, and on-line research is becoming the mainstream for astronomy, individual research based on locally hosted data is still very common. With the increase of personal storage capacity, it is easy to find hundreds to thousands of FITS files in the personal computer of an astrophysicist. Because Flexible Image Transport System (FITS) is a professional data format initiated by astronomers and used mainly in the small community, data management toolkits for FITS files are very few. Astronomers need a powerful tool to help them manage their local astronomical data. Although Virtual Observatory (VO) is a network oriented astronomical research environment, its applications and related technologies provide useful solutions to enhance the management and utilization of astronomical data hosted in an astronomer’s personal computer. FITSManager is such a tool to provide astronomers an efficient management and utilization of their local data, bringing VO to astronomers in a seamless and transparent way. FITSManager provides fruitful functions for FITS file management, like thumbnail, preview, type dependent icons, header keyword indexing and search, collaborated working with other tools and on-line services, and so on. The development of the FITSManager is an effort to fill the gap between management and analysis of astronomical data.     

A study of the Sunyaev–Zel'dovich increment using archival SCUBA data

In a search for evidence of the short wavelength increment in the Sunyaev–Zel'dovich (SZ) effect, we have analysed archival galaxy cluster data from the Submillimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope, resulting in the most complete pointed survey of clusters at 850 μm to date. SCUBA's 850-μm passband overlaps the peak of the SZ increment. The sample consists of 44 galaxy clusters in the range 0 < z < 1.3. Maps of each of the clusters have been made and sources have been extracted; as an ancillary product, we generate the most thorough galaxy cluster point source list yet from SCUBA. 17 of these clusters are free of obvious active galactic nuclei (AGN) and have data deep enough to provide interesting measurements of the expected SZ signal. Specialized analysis techniques are employed to extract the SZ effect signal from these SCUBA data, including using SCUBA's short wavelength band as an atmospheric monitor and fitting the long wavelength channel to a model of the spatial distribution of each cluster's SZ effect. By explicitly excising the exact cluster centre from our analysis, we demonstrate that emission from galaxies within the cluster does not contaminate our measurement. The SZ amplitudes from our measurements are consistently higher than the amplitudes inferred from low-frequency measurements of the SZ decrement.     

Precision in determination of astronomical refraction from aerological data

Various errors in determination of the local pure astronomical refraction are evaluated versus the apparent zenith distance z₀. Numerical integration with the step imposed by heights of an aerological sounding brings the error smaller than 0″01 until z₀ = 70°. For larger zenith distances integration with a more dense step is possible after fitting the data to a five-parameter functional dependence of the refractive index on height. The fitting is simultaneously a good equalization of aerological data reducing considerably their experimental error as well as short-term local fluctuations of the atmosphere. After equalization, the error in the refraction originating from the error in the aerological data is found to approach 0″01 at z₀ = 72°, 0″1 at z₀ = 82°, 1″ at z₀ = 87°, and 10″ at the horizon. This has to be taken into account when considering systematic deviations of the local pure refraction from that determined in a standard way. The purely stochastic error in the refraction originating in the error of the refractive index at the observation site is discussed within the context of local fluctuations of the atmosphere. It is evaluated that until z₀ = 85° the precision in determining the astronomical refraction in a single observation is limited by refraction anomalies (image motion) and only above 85° the error in aerological data becomes more important.     

TIRCAM: A mid-IR camera for astronomical imaging

We present the main characteristics of a new mid-IR camera, TIRCAM, operating at the 1.5 m Italian Infrared Telescope.     

Leveraging data lineage to infer logical relationships between astronomical catalogs

A novel method to infer logical relationships between sets is presented. These sets can be any collection of elements, for example astronomical catalogs of celestial objects. The method does not require the contents of the sets to be known explicitly. It combines incomplete knowledge about the relationships between sets to infer a priori unknown relationships. Relationships between sets are represented by sets of Boolean hypercubes. This leads to deductive reasoning by application of logical operators to these sets of hypercubes. A pseudo code for an efficient implementation is described. The method is used in the Astro-WISE information system to infer relationships between catalogs of astronomical objects. These catalogs can be very large and, more importantly, their contents do not have to be available at all times. Science products are stored in Astro-WISE with references to other science products from which they are derived, or their dependencies. This creates a full data lineage that links every science product all the way back to the raw data. Catalogs are created in a way that maximizes knowledge about their relationship with their dependencies. The presented algorithm is used to determine which objects a catalog represents by leveraging this information.     

Radio-silent isolated neutron stars as a new astronomical reality

Summary. As of today, seven X-ray sources have been tentatively identified as radio-quiet, isolated neutron stars. The family appears to be a rapidly growing one, although not all the objects have been identified with the same degree of certainty. The most convincing example of radio quiet pulsar is certainly Geminga, the neutron star nature of which, proposed in 1983 on the basis of its similarity with the Vela pulsar, has been firmly established with the discovery of its X and pulsation. Four more neutron star candidates, originally found in the Einstein data, have been confirmed by ROSAT, which has added to the list two more entries. All this is not the result of an unbiased search. The seven sources were not selected at random: four are inside supernova remnants, an obvious place to search for isolated neutron stars, while the remaining three were singled out because of some peculiarity. Intense -ray emission in the case of Geminga, very high X-ray counting rate for RXJ185635-3754, or being the brightest unidentified source in the Einstein medium sensitivity survey, MS 0317-6647. In spite of the limited number of objects and of the observational biases, these seven radio quiet neutron star candidates add valuable pieces of information to the observational panorama of known pulsars. Their properties, inferred from the X-ray emission, offer a coherent picture, pointing towards thermally emitting, cooling neutron stars. Received: April 1, 1996     

On the reduction and presentation of data in astronomical two-channel photopolarimetry

Many different methods exist for reducing data obtained when an astronomical source is studied with a two-channel polarimeter, such as a Wollaston prism system. This paper presents a rigorous method of reducing the data from raw aperture photometry, and evaluates errors both by a statistical treatment, and by propagating the measured sky noise from each frame. The reduction process performs a hypothesis test for the presence of linear polarization. The probability of there being a non-zero polarization is obtained, and the best method of obtaining the normalized Stokes Parameters is discussed. Point and interval estimates are obtained for the degree of linear polarization, which is subject to positive bias; and the polarization axis is found.     

Super resolution for astronomical observations

In order to obtain detailed information from multiple telescope observations a general blind super-resolution (SR) reconstruction approach for astronomical images is proposed in this paper. A pixel-reliability-based SR reconstruction algorithm is described and implemented, where the developed process incorporates flat field correction, automatic star searching and centering, iterative star matching, and sub-pixel image registration. Images captured by the 1-m telescope at Yunnan Observatory are used to test the proposed technique. The results of these experiments indicate that, following SR reconstruction, faint stars are more distinct, bright stars have sharper profiles, and the backgrounds have higher details; thus these results benefit from the high-precision star centering and image registration provided by the developed method. Application of the proposed approach not only provides more opportunities for new discoveries from astronomical image sequences, but will also contribute to enhancing the capabilities of most spatial or ground-based telescopes.     

Tests for spatial isotropy of three thousand gamma-ray bursts found in BATSE archival data

We apply isotropy tests to our new uniform catalog of cosmic gamma-ray bursts (GRBs) (Stern and Tikhomirova 1999). The catalog contains trigger and nontrigger bursts found in 1024-ms BATSE records over seven years. Based on this catalog, we confirm isotropy of the GRB spatial distribution for a sample that surpasses previous samples in size (2934 bursts) and in achieved threshold (fluxes down to 0.1 phot. cm^?2 s^?1, which is a factor of ～2 lower than the BATSE trigger threshold). We also confirm that there is no excess of bursts toward the galaxy M 31.     

A fast Bayesian approach to discrete object detection in astronomical data sets – PowellSnakes I

A new fast Bayesian approach is introduced for the detection of discrete objects immersed in a diffuse background. This new method, called PowellSnakes, speeds up traditional Bayesian techniques by (i) replacing the standard form of the likelihood for the parameters characterizing the discrete objects by an alternative exact form that is much quicker to evaluate; (ii) using a simultaneous multiple minimization code based on Powell's direction set algorithm to locate rapidly the local maxima in the posterior and (iii) deciding whether each located posterior peak corresponds to a real object by performing a Bayesian model selection using an approximate evidence value based on a local Gaussian approximation to the peak. The construction of this Gaussian approximation also provides the covariance matrix of the uncertainties in the derived parameter values for the object in question. This new approach provides a speed up in performance by a factor of '100' as compared to existing Bayesian source extraction methods that use Monte Carlo Markov chain to explore the parameter space, such as that presented by Hobson & McLachlan. The method can be implemented in either real or Fourier space. In the case of objects embedded in a homogeneous random field, working in Fourier space provides a further speed up that takes advantage of the fact that the correlation matrix of the background is circulant. We illustrate the capabilities of the method by applying to some simplified toy models. Furthermore, PowellSnakes has the advantage of consistently defining the threshold for acceptance/rejection based on priors which cannot be said of the frequentist methods. We present here the first implementation of this technique (version I). Further improvements to this implementation are currently under investigation and will be published shortly. The application of the method to realistic simulated Planck observations will be presented in a forthcoming publication.     

A method of astronomical autonomous orbit and attitude determinations for satellites

A method of realtime autonomous orbit determination for earth satellites using the extended Kalman filtering is proposed. The observed quantities are: the satellite-sun direction vector measured by a sun sensor, the satellite-earth and satellite-moon direction vectors measured by an ultraviolet sensor, and the geocentric distance measured by a radar altimeter. At the same time the satellite attitude to the earth is also determined. Results of our simulation of the autonomous orbit determination show that the precision of the orbit determinations is better than 200 m. The effects of the sampling period, orbital inclination, orbital eccentricity and orbital altitude on the precision of orbit determination are analyzed and compared, and certain principles helpful for improving the precision of orbit determination are suggested.