Space-based multi-band astronomical Variable Objects Monitor (SVOM)

Launch Date: June 22, 2024

Anticipated Start of Science Operations: February 2025

End of Operations: Mission duration of 3 years

Notices Archive: SVOM French Science Center

The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a French-Chinese mission, result of a collaboration between the two national space agencies, China National Space Administration (CNSA) and Centre national d'études spatiales (CNES). SVOM is dedicated to the study of the most powerful transient phenomena, with a particular emphasis on gamma-ray bursts (GRBs).

The SVOM spacecraft carries four multi-wavelength instruments: ECLAIRs, Gamma Ray burst Monitor (GRM), Microchannel X-ray Telescope (MXT) and Visible Telescope (VT). ECLAIRs and GRM can detect gamma-ray transient sources in real-time with localization capabilities for ECLAIRs. SVOM can transfer the alerts in near real-time with a typical latency of less than 30s and perform autonomous slew to allow x-ray and optical follow-up of the source with the smaller field of view instruments: MXT and VT.

Instruments	Energy Range	Field of View	Localization
ECLAIRs	4 - 250 keV	2 ster	~10ʹ radius (statistical + systematic)
GRM	15 - 5000 keV	2.6 ster	~10 degrees
MXT	0.2 - 10 keV	1.1° x 1.1°	~10-100ʺ radius (statistical + systematic)
VT	450 - 650 nm (Blue band) 650 - 1000 nm (Red band)	26ʹ x 26'	~1ʺ radius

GCN Kafka topics

SVOM distributes alerts and localizations of gamma-ray burst and other transients. For now, these notices are published only in VOEvent format through the GCN Kafka topics prefixed gcn.notices.svom.voevent.

Each of the four instruments has its own dedicated topic to stream notices with their related information. See table below:

Kafka topic	Notice types
`gcn.notices.svom.voevent.grm`	`grm-trigger`
`gcn.notices.svom.voevent.eclairs`	`eclairs-wakeup` `eclairs-catalog` `slewing` / `not-slewing`
`gcn.notices.svom.voevent.mxt`	`mxt-initial` `mxt-update`
`gcn.notices.svom.voevent.vt`	Available soon

VOEvent XML-serialized GCN notice types

Notice Type	Content	Latency
`grm-trigger`	GRM trigger notice with possible rough localization	~15 sec
`eclairs-wakeup`	ECLAIRs localization of a GRB candidate	~15 sec
`eclairs-catalog`	ECLAIRs localization of a flaring source from the on-board catalogue	~15 sec
`slewing` / `not-slewing` ¹	Platform slew status and target coordinates	~1-8 min
`mxt-initial_qf#`²	MXT localization of a found counterpart (only if platform slews)	~3 min
`mxt-update_qf#`²	MXT updated localization (qf > mxt-initial_qf)	~3 min

¹ not-slewingare published either if the detection did not reach the slew threshold (in a maximum time window of 8 min) or if the slew was not possible. The reason is specified in the notice parameters.

² the value of the quality factor qf indicates the accuracy of the localization:

qf1→ 120'' < R90 < 300''
qf2→ 60'' < R90 < 120''
qf3→ 30'' < R90 < 60''
qf4→ R90 < 30''

VOEvent examples

The complete list of published notices can be found here. Here are 3 different examples of SVOM VOEvent notices:

eclairs-wakeup

<?xml version='1.0' encoding='UTF-8'?>
<voe:VOEvent
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:voe="http://www.ivoa.net/xml/VOEvent/v2.0"
  xsi:schemaLocation="http://www.ivoa.net/xml/VOEvent/v2.0 http://www.ivoa.net/xml/VOEvent/VOEvent-v2.0.xsd"
  version="2.0"
  role="observation"
  ivorn="ivo://org.svom/fsc#sbYYMMDDnn_eclairs-wakeup">
  <Who>
    <AuthorIVORN>ivo://org.svom/FSC</AuthorIVORN>
    <Author>
        <title>SVOM French Science Center</title>
        <shortName>FSC</shortName>
        <contactName>Timothe Roland</contactName>
        <contactEmail>svom-contact@cea.fr</contactEmail>
    </Author>
    <Date>2022-04-04T11:54:42</Date>
  </Who>
  <What>
    <Param name="Packet_Type"  value="202"/>
    <Param name="Pkt_Ser_Num"  value="1"/>
    <Param name="Instrument"   value="ECLAIRs"  ucd="instr"/>
    <Group name="Svom_Identifiers">
      <Param name="Notice_Level"  value="N1e"         ucd="meta.code.class"/>
      <Param name="Burst_Id"      value="sbYYMMDDnn"  ucd="meta.id"/>
    </Group>
    <Group name="Detection_Info">
      <Param name="SNR"                value="6.58"  unit="sigma"     ucd="stat.snr"/>
      <Param name="Time_Window_Start"  value="2022-04-04T11:54:30.2Z" ucd="time.start"/>
      <Param name="Time_Window_End"    value="2022-04-04T11:54:32.2Z" ucd="time.end"/>
      <Param name="Timescale"          value="2"     unit="s"         ucd="time.interval"/>
      <Param name="Lower_Energy_Bound" value="4"     unit="keV"       ucd="em.energy"/>
      <Param name="Upper_Energy_Bound" value="50"    unit="keV"       ucd="em.energy"/>
      <Param name="Trigger_Type"       value="count_rate"             ucd="instr.param"/>
    </Group>
    <Group name="Target_Info">
      <Param name="Galactic_Lon"  value="332.72"  unit="deg"  ucd="pos.galactic.lon"/>
      <Param name="Galactic_Lat"  value="-21.46"  unit="deg"  ucd="pos.galactic.lat"/>
      <Param name="Sun_Angle"     value="49.58"   unit="deg"  ucd="pos.angDistance"/>
      <Param name="Moon_Angle"    value="128.6"   unit="deg"  ucd="pos.angDistance"/>
    </Group>
    <Group name="Satellite_Info">
      <Param name="Slew_Status"          value="not_requested"       ucd="meta.code.status"/>
      <Param name="Sat_Attitude_Ra"      value="2.36"    unit="deg"  ucd="pos.eq.ra"/>
      <Param name="Sat_Attitude_Dec"     value="148.22"  unit="deg"  ucd="pos.eq.de"/>
      <Param name="Sat_Attitude_Roll"    value="63.22"   unit="deg"  ucd="pos.posAng"/>
      <Param name="Sat_Position_Lat"     value="39.97"   unit="deg"  ucd="pos.earth.lat"/>
      <Param name="Sat_Position_Lon"     value="116.39"  unit="deg"  ucd="pos.earth.lon"/>
      <Param name="Sat_Position_Height"  value="614"     unit="km"   ucd="pos.earth.altitude"/>
    </Group>
  </What>
  <WhereWhen>
    <ObsDataLocation>
      <ObservatoryLocation id="GEOLEO"/>
      <ObservationLocation>
        <AstroCoordSystem id="UTC-FK5-GEO"/>
        <AstroCoords coord_system_id="UTC-FK5-GEO">
          <Time unit="s">
            <TimeInstant>
              <ISOTime>2022-04-04T11:54:30.2</ISOTime>
            </TimeInstant>
          </Time>
          <Position2D unit="deg">
            <Name1>RA</Name1>
            <Name2>Dec</Name2>
            <Value2>
              <C1>50.4488</C1>
              <C2>10.0041</C2>
            </Value2>
            <Error2Radius>0.2</Error2Radius>
          </Position2D>
        </AstroCoords>
      </ObservationLocation>
    </ObsDataLocation>
  </WhereWhen>
  <Why importance="0.7">
    <Inference probability="0.7">
      <Concept>process.variation.burst;em.gamma</Concept>
    </Inference>
  </Why>
  <How>
    <Description>N1e notice, data from ECLAIRs instrument</Description>
    <Reference uri="https://www.svom.eu/en/telescope-eclairs-en"/>
  </How>
</voe:VOEvent>

grm-trigger

<?xml version="1.0" encoding="UTF-8"?>
<voe:VOEvent
  xmlns:voe="http://www.ivoa.net/xml/VOEvent/v2.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.ivoa.net/xml/VOEvent/v2.0 http://www.ivoa.net/xml/VOEvent/VOEvent-v2.0.xsd"
  version="2.0"
  role="observation"
  ivorn="ivo://org.svom/fsc#sb25020701_grm-trigger">
  <Who>
    <AuthorIVORN>ivo://org.svom/FSC</AuthorIVORN>
    <Date>2025-02-07T07:14:22</Date>
    <Author>
      <title>SVOM French Science Center</title>
      <shortName>FSC</shortName>
      <contactName>Timothe Roland</contactName>
      <contactEmail>svom-contact@cea.fr</contactEmail>
    </Author>
  </Who>
  <What>
    <Param name="Packet_Type"  value="201"  ucd="meta.id"/>
    <Param name="Pkt_Ser_Num"  value="1"    ucd="meta.id"/>
    <Param name="Instrument"   value="GRM"  ucd="instr"/>
    <Group name="Svom_Identifiers">
      <Param name="Notice_Level"  value="N1g"         ucd="meta.id"/>
      <Param name="Burst_Id"      value="sb25020701"  ucd="meta.id"/>
    </Group>
    <Group name="Detection_Info">
      <Param name="SNR"                value="9.20"   unit="sigma"      ucd="stat.snr"/>
      <Param name="Timescale"          value="4.0"    unit="s"          ucd="time.interval"/>
      <Param name="Time_Window_Start"  value="2025-02-07T07:14:06.000Z" ucd="time.start"/>
      <Param name="Time_Window_End"    value="2025-02-07T07:14:10.000Z" ucd="time.end"/>
      <Param name="Lower_Energy_Bound" value="14.23"  unit="keV"        ucd="em.energy"/>
      <Param name="Upper_Energy_Bound" value="31.31"  unit="keV"        ucd="em.energy"/>
      <Param name="Triggered_GRDs"     value="101"                      ucd="instr.param"/>
    </Group>
    <Group name="Satellite_Info">
      <Param name="Attitude_Ra"    value="148.96"  unit="deg"  ucd="instr.param"/>
      <Param name="Attitude_Dec"   value="-17.74"  unit="deg"  ucd="instr.param"/>
      <Param name="Attitude_Roll"  value="194.06"  unit="deg"  ucd="instr.param"/>
    </Group>
  </What>
  <WhereWhen>
    <ObsDataLocation>
      <ObservatoryLocation id="GEOLEO"/>
      <ObservationLocation>
        <AstroCoordSystem id="UTC-ICRS-GEO"/>
        <AstroCoords coord_system_id="UTC-ICRS-GEO">
          <Time unit="s">
            <TimeInstant>
              <ISOTime>2025-02-07T07:14:06</ISOTime>
            </TimeInstant>
          </Time>
        </AstroCoords>
      </ObservationLocation>
    </ObsDataLocation>
  </WhereWhen>
  <Why importance="0.61">
    <Inference probability="0.61">
      <Concept>process.variation.burst;em.gamma</Concept>
    </Inference>
  </Why>
  <How>
    <Description>N1g notice, data from GRM</Description>
    <Reference uri="https://www.svom.eu/en/grm-gamma-ray-burst-monitor-en/"/>
  </How>
</voe:VOEvent>

mxt-initial_qf1

<?xml version="1.0" encoding="UTF-8"?>
<voe:VOEvent
  xmlns:voe="http://www.ivoa.net/xml/VOEvent/v2.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.ivoa.net/xml/VOEvent/v2.0 http://www.ivoa.net/xml/VOEvent/VOEvent-v2.0.xsd"
  version="2.0"
  role="observation"
  ivorn="ivo://org.svom/fsc#sb25020504_mxt-initial_qf1">
  <Who>
    <AuthorIVORN>ivo://org.svom/FSC</AuthorIVORN>
    <Date>2025-02-05T21:41:59</Date>
    <Author>
      <title>SVOM French Science Center</title>
      <shortName>FSC</shortName>
      <contactName>Timothe Roland</contactName>
      <contactEmail>svom-contact@cea.fr</contactEmail>
    </Author>
  </Who>
  <What>
    <Param name="Packet_Type" value="209" ucd="meta.id"/>
    <Param name="Pkt_Ser_Num" value="1"   ucd="meta.id"/>
    <Param name="Instrument"  value="MXT" ucd="instr"/>
    <Group name="Svom_Identifiers">
      <Param name="Notice_Level"  value="N2m"        ucd="meta.id"/>
      <Param name="Burst_Id"      value="sb25020504" ucd="meta.id"/>
    </Group>
    <Group name="Detection_Info">
      <Param name="SNR"        value="92.00" unit="sigma"          ucd="stat.snr"/>
      <Param name="Mean_Flux"  value="0.43"  unit="erg.cm^-2.s^-1" ucd="phot.flux"/>
      <Param name="Flux_Error" value="0.66"  unit="erg.cm^-2.s^-1" ucd="phot.flux"/>
    </Group>
    <Group name="Target_Info">
      <Param name="Within_ECLAIRs_R90" value="False"                ucd="instr.param"/>
      <Param name="ECLAIRs_Angle"      value="2.46"   unit="arcmin" ucd="pos.angDistance"/>
      <Param name="Galactic_Lon"       value="186.88" unit="deg"    ucd="pos.galactic.lon"/>
      <Param name="Galactic_Lat"       value="22.52"  unit="deg"    ucd="pos.galactic.lat"/>
      <Param name="Moon_Angle"         value="55.52"  unit="deg"    ucd="pos.angDistance"/>
      <Param name="Sun_Angle"          value="151.19" unit="deg"    ucd="pos.angDistance"/>
    </Group>
    <Group name="Satellite_Info">
      <Param name="Use_VT_Attitude" value="True"              ucd="instr.param"/>
      <Param name="Attitude_Ra"     value="139.61" unit="deg" ucd="instr.param"/>
      <Param name="Attitude_Dec"    value="16.30"  unit="deg" ucd="instr.param"/>
      <Param name="Attitude_Roll"   value="344.09" unit="deg" ucd="instr.param"/>
    </Group>
  </What>
  <WhereWhen>
    <ObsDataLocation>
      <ObservatoryLocation id="GEOLEO"/>
      <ObservationLocation>
        <AstroCoordSystem id="UTC-ICRS-GEO"/>
        <AstroCoords coord_system_id="UTC-ICRS-GEO">
          <Time unit="s">
            <TimeInstant>
              <ISOTime>2025-02-05T21:34:31.974000</ISOTime>
            </TimeInstant>
          </Time>
          <Position2D unit="deg">
            <Name1>RA</Name1>
            <Name2>Dec</Name2>
            <Value2>
              <C1>113.4980</C1>
              <C2>32.3892</C2>
            </Value2>
            <Error2Radius>0.0356</Error2Radius>
          </Position2D>
        </AstroCoords>
      </ObservationLocation>
    </ObsDataLocation>
  </WhereWhen>
  <Why importance="1.00">
    <Inference probability="1.00">
      <Concept>process.variation.burst;em.gamma</Concept>
    </Inference>
  </Why>
  <How>
    <Description>N2m notice, data from MXT</Description>
    <Reference uri="https://www.svom.eu/en/mxt-microchannel-x-ray-telescope-en/"/>
  </How>
  <Citations>
    <EventIVORN cite="followup">ivo://org.svom/fsc#sb25020504_eclairs-refined</EventIVORN>
    <EventIVORN cite="followup">ivo://org.svom/fsc#sb25020504_slewing</EventIVORN>
  </Citations>
</voe:VOEvent>

Yearly Trigger Rates

Instrument	Type	Yearly Rates
ECLAIRs	GRBs	60 GRBs/yr
GRM	GRBs	130 GRBs/yr