24,725 research outputs found
HATSouth: a global network of fully automated identical wide-field telescopes
HATSouth is the world's first network of automated and homogeneous telescopes
that is capable of year-round 24-hour monitoring of positions over an entire
hemisphere of the sky. The primary scientific goal of the network is to
discover and characterize a large number of transiting extrasolar planets,
reaching out to long periods and down to small planetary radii. HATSouth
achieves this by monitoring extended areas on the sky, deriving high precision
light curves for a large number of stars, searching for the signature of
planetary transits, and confirming planetary candidates with larger telescopes.
HATSouth employs 6 telescope units spread over 3 locations with large longitude
separation in the southern hemisphere (Las Campanas Observatory, Chile; HESS
site, Namibia; Siding Spring Observatory, Australia). Each of the HATSouth
units holds four 0.18m diameter f/2.8 focal ratio telescope tubes on a common
mount producing an 8.2x8.2 arcdeg field, imaged using four 4Kx4K CCD cameras
and Sloan r filters, to give a pixel scale of 3.7 arcsec/pixel. The HATSouth
network is capable of continuously monitoring 128 square arc-degrees. We
present the technical details of the network, summarize operations, and present
weather statistics for the 3 sites. On average each of the 6 HATSouth units has
conducted observations on ~500 nights over a 2-year time period, yielding a
total of more than 1million science frames at 4 minute integration time, and
observing ~10.65 hours per day on average. We describe the scheme of our data
transfer and reduction from raw pixel images to trend-filtered light curves and
transiting planet candidates. Photometric precision reaches ~6 mmag at 4-minute
cadence for the brightest non-saturated stars at r~10.5. We present detailed
transit recovery simulations to determine the expected yield of transiting
planets from HATSouth. (abridged)Comment: 25 pages, 11 figures, 1 table, submitted to PAS
Timely Monitoring of Dynamic Sources with Observations from Multiple Wireless Sensors
Age of Information (AoI) has recently received much attention due to its
relevance in IoT sensing and monitoring applications. In this paper, we
consider the problem of minimizing the AoI in a system in which a set of
sources are observed by multiple sensors in a many-to-many relationship, and
the probability that a sensor observes a source depends on the state of the
source. This model represents many practical scenarios, such as the ones in
which multiple cameras or microphones are deployed to monitor objects moving in
certain areas. We formulate the scheduling problem as a Markov Decision
Process, and show how the age-optimal scheduling policy can be obtained. We
further consider partially observable variants of the problem, and devise
approximate policies for large state spaces. Our evaluations show that the
approximate policies work well in the considered scenarios, and that the fact
that sensors can observe multiple sources is beneficial, especially when there
is high uncertainty of the source states.Comment: Submitted for publicatio
Optimal Status Updates for Minimizing Age of Correlated Information in IoT Networks with Energy Harvesting Sensors
Many real-time applications of the Internet of Things (IoT) need to deal with
correlated information generated by multiple sensors. The design of efficient
status update strategies that minimize the Age of Correlated Information (AoCI)
is a key factor. In this paper, we consider an IoT network consisting of
sensors equipped with the energy harvesting (EH) capability. We optimize the
average AoCI at the data fusion center (DFC) by appropriately managing the
energy harvested by sensors, whose true battery states are unobservable during
the decision-making process. Particularly, we first formulate the dynamic
status update procedure as a partially observable Markov decision process
(POMDP), where the environmental dynamics are unknown to the DFC. In order to
address the challenges arising from the causality of energy usage, unknown
environmental dynamics, unobservability of sensors'true battery states, and
large-scale discrete action space, we devise a deep reinforcement learning
(DRL)-based dynamic status update algorithm. The algorithm leverages the
advantages of the soft actor-critic and long short-term memory techniques.
Meanwhile, it incorporates our proposed action decomposition and mapping
mechanism. Extensive simulations are conducted to validate the effectiveness of
our proposed algorithm by comparing it with available DRL algorithms for
POMDPs
- …