Night Sky Live

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Night Sky Live!
All-Sky Transient Detection Using the Night Sky
Live! Network Lior Shamir Robert J.
Nemiroff Abstract Real-time detection of optical
transients has an important role in modern
astronomy. However, with the absence of a
sustainable system constantly monitoring the
entire sky, one can reasonably assume that many
of the short timescale transients are not
reported. Covering 90 of the global night sky
at any given time, the Night Sky Live all-sky
monitoring network provides an infrastructure
capable of transient detection at real-time. The
system takes an all-sky exposure every 236
seconds, rejects cosmic ray hits and bright
planets and searches for optical transients by
comparing the exposure to a canonical frame taken
at the same sidereal time. The system alerts on
persistent transients that rotate with the sky
for at least 12 minutes (3 NSL exposures), or
transients that are detected simultaneously by
several Night Sky Live nodes covering the same
portion of the sky. Currently, the Night Sky Live
network can detect 5th magnitude optical
transient.
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Night Sky Live!
The Night Sky Live network is capable of creating
a continuous record of the nighttime optical sky.
Fully 2p steradians -- half the sky -- are
monitored passively, without tracking. Currently,
we have built and deployed 10 CONtinuous CAMeras
(CONCAMs) at many of the world's premier
observatories that together compose the Night Sky
Live (NSL) network and provide continuous
coverage for much of the nighttime sky. CONCAMs
take 180-second exposures picture every 3 minutes
and 56 seconds, and can detect stars down to
visual magnitude 6.8 near the image center.
CONCAMs provide near real-time pictures of the
night sky, and have computers that process the
images into additional information such as
photometry analysis of the frames and all-sky
atmospheric opacity maps. All images and files
are uploaded to a main server, where they are
archived and accessible to the public.
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Night Sky Live!
A panoramic image of the whole night sky is
captured every 236 seconds using a super-wide
angle fish-eye lens.
The FITS all-sky images captured by a CCD camera
are sent over the internet to NightSkyLive.net
server at Michigan Tech.
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Night Sky Live!
Fuzzy Logic Model
Using a fuzzy logic model celestial coordinates
are transformed into image coordinates. This
transformation enables the rejection of planets
and variable stars.
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Night Sky Live!
All-Sky Image
Fuzzy Logic-Based Cosmic Ray Hit Rejection
Canonical Image Database
Bright Planets and Variable Stars (dMgt1) Rejection
Comparison with a Set of Canonical Frames Taken
at the Same Sidereal Time
Transients
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Night Sky Live!
Canonical Image Database

• Images are added to the canonical image
  database based on the following algorithm
• Find all point spread functions in the image
• Search the point spread functions of all stars
  brighter than 5.2 (V-mag) that should appear in
  the sky at the time the image was taken.
• If the PSFs of 96 of the stars are found, the
  image is added to the database.

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Night Sky Live!
Alert Criteria
Transients are alerted if they persist for 2
consecutive frames (8 minutes), or detected By
more than one CONCAM station at the same
time. Geocentric coordinates of transients from
different stations are compared, and an alert is
triggered in case of a match. Transients 40s
brighter than their local background are alerted.
This criterion is comparable to 5.5 visual
magnitude in CONCAM3 systems.
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Geosynchronous Satellites
Night Sky Live!
The picture shows a bright transient caused by a
geosynchronous satellite recorded in Canary
Islands. The transient is of visual magnitude 2,
and appeared in the sky for approximately 12
minutes (3 consecutive frames). In the period
between September 16th 2003 and October 13th
2003, the transient appeared every day at the
time and at the same location in the sky.
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Geosynchronous Satellites
Night Sky Live!
The transient recorded by both Haleakala and
Mauna Kea CONCAMs at the same time and at the
same region of the sky. The visual magnitude of
the object was 2.5, and the duration of the
flash was around 15 minutes.
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Geosynchronous Satellites
Night Sky Live!
Further investigation turned up that the flashing
object is probably the satellite Superbird A,
a failed Japanese communication satellite. In
the period between October 8th 2004 and October
19th 2004, the bright glint appeared every day at
657 UT. Other periodic transients caused by
geosynchronous satellites have been recorded in
Mauna Kea, Haleakala, Canary Islands and Kitt
Peak. We discovered that each of the
observatories recorded at least one bright
(visual magnitude 2) gt8 minutes glint from a
geosynchronous satellite every day.
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Other Satellites
Night Sky Live!
NSL is capable of alerting other bright
satellites glints such as Iridium satellites,
HST, ISS, etc. The system can differentiate
between short glints and longer glints (gt 4
minutes).
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Education
Night Sky Live!
The Night Sky Live infrastructure allows
graduate, undergraduate and amateur astronomers
to search for satellite glints, meteors and
optical transients by writing their own
customized software, using the software provided
by NSL and even by observing the Night Sky Live
images by eye. Students can learn the notion of
optical transients by observing and studying the
different types of celestial flashes such as HST,
IIS, geosynchronous satellites and meteors.
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Available Educational ModulesAll modules (pdf
format) can be downloaded at http//nightskylive.n
et/education
Night Sky Live!
The Variability of Polaris Students are required
to show that Polaris is a variable star by
analyzing a series of measurements of the
luminosity of Polaris. Students compare
measurements taken at the same sidereal time and
use statistical methods to achieve their goal.
Astrometry of Meteoroids Introductory Astronomy
Lab Exercise
The Variability of Polaris Introductory Astronomy
Lab Exercise
Department of Physics Michigan Technological
University 1400 Townsend Dr. Houghton, MI 49931
Astrometry of Meteoroids Students are required to
analyze the trajectory of meteors recorded
simultaneously in two different observatories.
Students first analyze the images to find a
meteor trail, and then use parallax in order to
obtain the altitude, direction, distance and the
absolute length of the luminous trail.
Department of Physics Michigan Technological
University 1400 Townsend Dr. Houghton, MI 49931
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Conclusions
Night Sky Live!

• Performing all-sky transient detection allows a
  systematic monitoring and detection of bright
  transient visible to the unaided eye.
• The search for optical transients can be
  disturbed by glints from satellites. For
  instance, the flash reported by (Halliday,
  Feldman Blackwell) in 1987 near the
  constellation Perseus appeared later to be a
  series of satellite glints (Schaefer et al.,
  1987). We found that bright (v2) and
  persistent (8 minutes or longer) glints from
  geosynchronous satellites are not rare, and
  approximately one such glint is expected each
  night.

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References
Night Sky Live!

• Shamir, L., A Fuzzy Logic-Based Algorithm for
  Cosmic-ray Hit Rejection From Single Images,
  2005, AN, in press
• Shamir, L., Nemiroff, R. J., A Fuzzy Logic Based
  Algorithm For Finding Astronomical Objects in
  Wide-Angle Frames, 2005, Publications of the
  Astronomical Society of Australia, Vol. 22(2), p.
  111-117, 2005
• Halliday, I., Feldman, P. A., Blackwell, A. T.,
  Evidence from meteor patrol photographs for a
  nonastronomical origin of the reported optical
  flashes in Perseus, 1987, ApJ, Vol. 320, p.
  153-155.
• Castro-Tirado et al., Detection of an optical
  transient following the 13 March 2000 short/hard
  gamma-ray burst, 2002, ApJ, Vol. 393, 55-59.
• Schaefer, B. E. et al., 1987, The Perseus Flasher
  and satellite glints, ApJ, Vol., 320, p. 398-404
• Schaefer, B. E., Pedersen, H., Gouiffes, C.,
  Poulsen, J. M., Pizzichini, G., 1987, Optical
  flash background rates, AAS, Vol. 174, p.
  338-343.