DART: Distribution Aware Retinal Transform for Event-based Cameras

We introduce a generic visual descriptor, termed as distribution aware retinal transform (DART), that encodes the structural context using log-polar grids for event cameras. The DART descriptor is applied to four different problems, namely object classification, tracking, detection and feature matching: (1) The DART features are directly employed as local descriptors in a bag-of-features classification framework and testing is carried out on four standard event-based object datasets (N-MNIST, MNIST-DVS, CIFAR10-DVS, NCaltech-101). (2) Extending the classification system, tracking is demonstrated using two key novelties: (i) For overcoming the low-sample problem for the one-shot learning of a binary classifier, statistical bootstrapping is leveraged with online learning; (ii) To achieve tracker robustness, the scale and rotation equivariance property of the DART descriptors is exploited for the one-shot learning. (3) To solve the long-term object tracking problem, an object detector is designed using the principle of cluster majority voting. The detection scheme is then combined with the tracker to result in a high intersection-over-union score with augmented ground truth annotations on the publicly available event camera dataset. (4) Finally, the event context encoded by DART greatly simplifies the feature correspondence problem, especially for spatio-temporal slices far apart in time, which has not been explicitly tackled in the event-based vision domain.Comment: 12 pages, revision submitted to TPAMI in Nov 201

Southern Hemisphere automated supernova search

The Perth Astronomy Research Group has developed an automated supernova search program, using the 61 cm Perth–Lowell reflecting telescope at Perth Observatory in Western Australia, equipped with a CCD camera. The system is currently capable of observing about 15 objects per hour, using 3 min exposures, and has a detection threshold of 18th–19th magnitude. The entire system has been constructed using low‐cost IBM‐compatible computers. Two original discoveries (SN 1993K, SN 1994R) have so far been made during automated search runs. This paper describes the hardware and software used for the supernova search program, and shows some preliminary results from the search system

The Taiwanese-American Occultation Survey: The Multi-Telescope Robotic Observatory

The Taiwanese-American Occultation Survey (TAOS) operates four fully automatic telescopes to search for occultations of stars by Kuiper Belt Objects. It is a versatile facility that is also useful for the study of initial optical GRB afterglows. This paper provides a detailed description of the TAOS multi-telescope system, control software, and high-speed imaging.Comment: 11 pages, 11 figure

GRAVITY: getting to the event horizon of Sgr A*

We present the second-generation VLTI instrument GRAVITY, which currently is in the preliminary design phase. GRAVITY is specifically designed to observe highly relativistic motions of matter close to the event horizon of Sgr A*, the massive black hole at center of the Milky Way. We have identified the key design features needed to achieve this goal and present the resulting instrument concept. It includes an integrated optics, 4-telescope, dual feed beam combiner operated in a cryogenic vessel; near infrared wavefront sensing adaptive optics; fringe tracking on secondary sources within the field of view of the VLTI and a novel metrology concept. Simulations show that the planned design matches the scientific needs; in particular that 10 microarcsecond astrometry is feasible for a source with a magnitude of K=15 like Sgr A*, given the availability of suitable phase reference sources.Comment: 13 pages, 11 figures, to appear in the conference proceedings of SPIE Astronomical Instrumentation, 23-28 June 2008, Marseille, Franc

Reanalysis of Data Taken by the CANGAROO 3.8 Meter Imaging Atmospheric Cherenkov Telescope: PSR B1706-44, SN 1006, and Vela

We have reanalyzed data from observations of PSR B1706-44, SN 1006, and the Vela pulsar region made with the CANGAROO 3.8 m imaging atmospheric Cherenkov telescope between 1993 and 1998 in response to the results reported for these sources by the H.E.S.S. collaboration. In our reanalysis, in which gamma-ray selection criteria have been determined exclusively using gamma-ray simulations and OFF-source data as background samples, no significant TeV gamma-ray signals have been detected from compact regions around PSR B1706-44 or within the northeast rim of SN 1006. We discuss reasons why the original analyses gave the source detections. The reanalysis did result in a TeV gamma-ray signal from the Vela pulsar region at the 4.5 sigma level using 1993, 1994, and 1995 data. The excess was located at the same position, 0.13 deg. to the southeast of the Vela pulsar, as that reported in the original analysis. We have investigated the effect of the acceptance distribution in the field of view of the 3.8 m telescope, which rapidly decreases toward the edge of the field of the camera, on the detected gamma-ray morphology. The expected excess distribution for the 3.8 m telescope has been obtained by reweighting the distribution of HESS J0835-455 measured by H.E.S.S. with the acceptance of the 3.8 m telescope. The result is morphologically comparable to the CANGAROO excess distribution, although the profile of the acceptance-reweighted H.E.S.S. distribution is more diffuse than that of CANGAROO. The integral gamma-ray flux from HESS J0835-455 has been estimated for the same region as defined by H.E.S.S. from the 1993-1995 data of CANGAROO to be F(> 4.0 +/- 1.6 TeV) = (3.28 +/- 0.92) x 10^{-12} photons cm^{-2} s^{-1}, which is statistically consistent with the integral flux obtained by H.E.S.S.Comment: Published in ApJ, minor improvement