Download A Heterogeneous Telescope Network

VOEvent
Sky Event Reporting Metadata
Authors:
Rob Seaman, National Optical Astronomy Observatory, USA
Roy Williams, California Institute of Technology, USA
Alasdair Allan, University of Exeter, UK
Scott Barthelmy, NASA Goddard Spaceflight Center, USA
Joshua Bloom, University of California, Berkeley, USA
Frederic Hessman, University of Gottingen, Germany
Szabolcs Marka, Columbia University, USA
Arnold Rots, Harvard-Smithsonian Center for Astrophysics, USA
Chris Stoughton, Fermi National Accelerator Laboratory, USA
Tom Vestrand, Los Alamos National Laboratory, USA
Robert White, LANL, USA
Przemyslaw Wozniak, LANL, USA
1
What is this VOEvent thing anyway?
• VOEvent defines the content and meaning of a
standard information packet for representing,
transmitting, publishing and archiving the discovery of
a transient celestial event, with the common
implication that timely follow-up is being requested.
IVOA Interoperability Meeting, Kyoto (May 2005)
2
Why would you want to do that?
• Providers of the event stream including the SWIFT and synoptic
surveys coming online now and planned for the future.
• There are robotic telescope networks that will respond in
seconds to these discovery events, giving a comprehensive,
panchromatic view.
• Until now, events have been distributed in various formats and
protocols, so that aggregation and federation have been difficult.
• The objective of the VOEvent working group is to build an open
standard for exchanging messages about these immediate
astronomical events, including publication, archiving, query,
subscription, and aggregation.
IVOA Interoperability Meeting, Kyoto (May 2005)
3
What VOEvent is not…
• A way to produce a phase zero description of an
telescope and instrument package.
• A way to build an document to request an
observation from a robotic telescope.
• For these cases you should use Remote Telescope
Markup Language (RTML), see
http://monet.uni-goettingen.de/twiki/bin/view/RTML
IVOA Interoperability Meeting, Kyoto (May 2005)
4
So what have we been doing?
• A preliminary VOEvent standard has been agreed in
rough form during the workshop at Cal Tech in April.
• Buy-in for the new standard from many places,
including: GCN, LSST, Pan-STARRS, PalomarQuest, LIGO, eSTAR, RAPTOR/TALON, PAIRITEL,
ATEL, and the Hands-On Universe (HOU) projects.
• We shalt not reinvent the wheel, but only market it…
IVOA Interoperability Meeting, Kyoto (May 2005)
5
Simplicity vs. rich semantic content
• Perhaps the major debate at the Caltech workshop
was the balance between simplicity and the richness
of the semantic content.
• If we make things too complex, even if ratified the
standard will not be adopted by the people who
matter, the event publishers.
• If we make things too light weight, even if adopted by
the event publishers, it will not be used by
consumers.
IVOA Interoperability Meeting, Kyoto (May 2005)
6
Who, What, Where, When & How
• A VOEvent document is divided in distinct sections
detailing the Who, What, WhereWhen and How of an
event.
• In addition there are also sections which deal with
Hypothesis, the initial scientific assessment of the
event…
• …plus Citations, which provide references to other
documents, and Description which contains human
readable content.
IVOA Interoperability Meeting, Kyoto (May 2005)
7
Adoption and integration…
• Adopted the IVOA Space-Time Coordinate (STC)
schema to represent.
• Integrated with Remote Telescope Markup Language
(RTML) so that VOEvent can both include instrument
descriptions, and form the basis of an RTML
document which can be used to drive robotic
telescopes.
• Make heavy use of references…
IVOA Interoperability Meeting, Kyoto (May 2005)
8
Citations and identifiers
• An VOEvent message includes a global identifier so
they can be cited in future messages,
<VOEvent id="ivo://raptor.lanl/23564/event4" role="actual" version="0.90" >
• Message typing, such as discovery, follow-up,
retraction and supersede to provide a coherent
picture of distributed knowledge about a discovery.
<Citations>
<EventID cite="followup">ivo://raptor.lanl/235649409</EventID>
<Description>This is animproved observation of the earlier event.</Description>
<Reference uri="http://raptor.lanl.gov/data/lightcurves/235649409" type="url” />
</Citations>
IVOA Interoperability Meeting, Kyoto (May 2005)
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Modular syntax
• We have built VOEvent in a modular manner…
• It can be parsed easily without special tools, although
special tools will allow you to get more semantic
content from the message.
• It should have easy to extend, however when dealing
with messages intended for real time operations it is
crucial to avoid complications and bloat.
IVOA Interoperability Meeting, Kyoto (May 2005)
10
UCDs and rich content
• A VOEvent message will try and provide rich
semantic content through the use of the IVOA UCD
standard to both express content in a provider neutral
manner…
• …and allow the messages to be automatically parsed
by software.
• Hope to push this forward by extending UCDs to
allow us to describe the scientific nature of the event,
or how it is changing with time.
IVOA Interoperability Meeting, Kyoto (May 2005)
11
A simple example
• This VOEvent packet is an imaginary report from the
Raptor project at Los Alamos, that a magnitude 13
star was seen at RA =148.888, Dec = 69.065, with an
error radius of 0.1 degrees.
• It is reported as "fast orphan optical transient", so we
infer that the same source was not seen in that
position before.
IVOA Interoperability Meeting, Kyoto (May 2005)
12
A simple example
<?xml version="1.0" encoding="UTF-8"?>
<VOEvent id="ivo://raptor.lanl/235649409/sn2005k" role="actual" version="0.90"
xmlns:stc="http://www.ivoa.net/xml/STC/stc-v1.22.xsd" xmlns:crd="http://www.ivoa.net/xml/STC/STCcoords/v1.22"
xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance”
xsi:schemaLocation="http://www.ivoa.net/xml/STC/stc-v1.22.xsd stc-v1.22.xsd">
<Curation>
<PublisherID>ivo://raptor.lanl/</PublisherID><Date>2005-04-15T14:34:16</Date>
</Curation>
<WhereWhen>
<stc:ObservationLocation>
<xi:include href="http://www.ivoa.net/xml/STC/FK5-UTC-TOPO.xml"/>
<crd:AstroCoords coord_system_id="FK5-UTC-TOPO">
<crd:Time unit="s>
<crd:TimeInstant><crd:ISOTime>2005-04-15T23:59:59</crd:ISOTime> </crd:TimeInstant>
</crd:Time>
<crd:Position2D unit="deg”>
<crd:Value2>148.888 69.065</crd:Value2><crd:Error2Radius>0.1</crd:Error2Radius>
</crd:Position2D>
</crd:AstroCoords>
</stc:ObservationLocation>
</WhereWhen>
<What>
<Param name="magnitude" ucd="phot.mag:em.opt.R" value="13.2" />
</What>
<Hypothesis>
<Classification probability="30"><Class>Fast Orphan Optical Transient</Class></Classification>
</Hypothesis>
</VOEvent>
IVOA Interoperability Meeting, Kyoto (May 2005)
13
A “typical” example
• Will be longer than the one shown. For instance it
may contain citations to other documents,
<Citations>
<EventID cite="followup">ivo://raptor.lanl/23569</EventID>
<Description>
This is an observation of the earlier event but with improved
square-galaxy discrimination.
</Description>
<Reference uri="http://raptor.lanl.gov/data/lightcurves/2356" type="url">
This is the light curve associated with the observation.
</Reference>
</Citations>
• … or more semantic content describing the event.
IVOA Interoperability Meeting, Kyoto (May 2005)
14
A redirection example
• The capability to distribute a very lightweight alert
consisting of a pointer to a stored event packet. The
ID is set to that of the original packet, allowing an
intervening client such as an aggregator to persist the
message in a backend database.
<?xml version="1.0" encoding="UTF-8"?>
<VOEvent id="ivo://raptor.lanl/235649409/sn2005k" role="actual" version="0.90">
<Reference uri="http://www.raptor.lanl.gov/docs/event233.xml" type="voevent" />
</VOEvent>
IVOA Interoperability Meeting, Kyoto (May 2005)
15
Implementation
• Rick Hessman is hosting the collaborative schema
development at,
http://monet.uni-sw.gwdg.de/twiki/bin/view/VOEvent/
• Two reference implementations. One in Perl by the
eSTAR project, and the other in C++ by the RAPTOR
project.
• Software development hosted by Sourceforge at,
http://sourceforge.net/projects/voevent/
IVOA Interoperability Meeting, Kyoto (May 2005)
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Why are we telling you guys?
• We want your (fresh) brains, err, input…
• There is a VOEvent session in Conference Room K
on Thursday morning. You are invited to attend and
contribute, promise I won’t shout at you too much.
• Err, probably…
IVOA Interoperability Meeting, Kyoto (May 2005)
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In conclusion…
• There is an emerging standard, and this is the point
where you can make a real difference and influence
its evolution.
• An draft release of version 0.9 of the standards
document can be found at,
http://www.ivoa.net/internal/IVOA/IvoaVOEvent/VOEvent-0.90.html
http://www.ivoa.net/internal/IVOA/IvoaVOEvent/VOEvent-0.90.pdf
• Comments welcome…
IVOA Interoperability Meeting, Kyoto (May 2005)
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The HTN Workshop
July 18 -21 2005
Aims
• Interoperability between robotic
telescope networks
• Interoperability with the Virtual
Observatory (VO) for event
notification
• Establishment of an e-market for
the exchange of telescope time
See htn-workshop2005.ex.ac.uk
Science Goal Monitor
IVOA Interoperability Meeting, Kyoto (May 2005)