INTEGRAL Latest News

INTEGRAL does one of its fastest Target-of-Opportunity observations

14 October 2021 Demonstrating the recovery of the spacecraft from the critical anomaly on 22/23 September, INTEGRAL executed one of its fastest (4.7 hours from time of trigger to start of observation) re-planning and execution of a Target-of-Oportunity (ToO) observation in response to the new rise in X-rays from V4641 Sagittarii (SAX J1819.3-2525 = XTE J1819-254). Concurrent observations were carried out with Swift and NICER. First results are reported in The Astronomer's Telegram #14971. INTEGRAL will continue to observe the source in the next days, also in coordination with XMM-Newton.

INTEGRAL is back and Doing Science

01 October 2021 With the start of revolution 2418 this morning INTEGRAL returned to routine pre-planned operations. The Science Operations window opened at 12:19 UT. All spacecraft subsystems and instruments are operating nominally.

Mission critical anomaly

29 September 2021 On Sep 22 around midday, a Single Event Upset (SEU) caused the switch off of reaction wheel 3, which then proceeded to slowly spin-down due to friction within its bearing. This transfer of momentum within the spacecraft resulted in an uncontrolled slew that eventually triggered the Emergency Safe Attitude Mode (ESAM), which unfortunately did not manage to stabilise the spacecraft due to a severe underperformance of the Reaction Control Subsystem (RCS). Reaction wheels were re-activated but, as the current control mode relied upon a fully functional RCS, the spacecraft kept spinning at a rate of about 10 deg/minute in at least two axes, and the wheels became saturated with angular momentum. Telemetry was choppy, coming in for short periods due to the spinning of the spacecraft, which made the analysis even harder. Batteries were discharging, with only short charging periods when the panels briefly faced the sun.

The first challenge was to decrease as much as possible the energy consumption in order to buy more time. First estimates of charge remaining before blackout and the loss of the satellite was 3 hours. Step by step, turning off various things, the time window was expanded to 5 or 6 hours. This gave the necessary time to turn to the second immediate challenge which was to try to stop the spinning.

To do that, the colleagues from MOC supported by industry experts analysed the parameters that defined the performance of the reaction wheels, and carefully built the stack of commands to manipulate the reaction wheels to slow down the body rates (spinning). In particular the spare reaction wheel 1 was activated to absorb some of the excess angular momentum on the other three wheels. In the late afternoon, the commands were sent and successfully reduced the spacecraft's rotation rate significantly. Everyone online breathed a huge sigh of relief.

The next steps were to again adjust the reaction wheel speeds to reduce the spin rate further and thus stabilise the spacecraft to allow a controlled rotation to a sun facing attitude and recharge of the batteries. In addition, the MOC engineers wanted to bring the reaction wheel speeds as close to zero as possible in order to have maximum flexibility in delicately balancing the angular momentum between the wheels.

This heroic effort of the exceptionally knowledgeable and skilled and experienced MOC engineers and industry experts continued into the early hours of the morning on Sep 23 until the spacecraft was placed in a favourable sun-facing and battery-charging attitude for perigee passage.

To everyone's surprise, upon perigee exit, the spacecraft was once again rotating with high reaction wheel speeds. The reason for this is still not completely understood. But with the experience of the previous day, the series of operations that were successfully performed on Sep 22 guided the steps to recovery, and within two and a half hours the spacecraft had been stabilised and its angular momentum control regained once more. To prevent this from happening again, the ESAM and AMD (autonomous momentum dump) that make use of the now unreliable thrusters were both deactivated. The spacecraft has since remained in a well-controlled state and stable angular momentum configuration.

On Sunday afternoon six slews were executed to perform a Z-flip in order to reduce angular momentum. Another set of manoeuvre was performed on Tuesday and Wednesday. Since Monday Sep 27 at 18:00, all systems are online and all instruments have been activated and are collecting data. So far the only known casualty following the events of last week is the OMC power supply converter A. The B converter is now in use and functions nominally. INTEGRAL is expected to be back on scheduled science targets by Friday Oct 1 following a full instrument health check-out.

There will be some lost science time from the anomaly that will cover the period from Sep 22 to 30. There were also a few hours of lost telemetry (TM) due to an anomaly experienced when switching between the two on-board low gain antennas (LGAs) on Sep 12 which impacted TM transmission. The problem was identified as possibly being linked to an issue while commanding the radio switch linking the transponder TX1 to the LGAs. For risk mitigation this radio switch is currently not used (nor is an existing redundant switch). Instead an on/off swap of the two redundant transponders TX1 and TX2 - that are both working fine - is used to activate one or other of the two LGAs. The details of the lost science time will be indicated in the scheduling pages.

Rescuing Integral: No thrust? No problem!

17 July 2021 A year ago, a failure on the Integral spacecraft meant it fired its thrusters for likely the last time. In the days since, the spacecraft in Earth orbit has continued to shed light on the violent gamma ray Universe, and it should soon be working even more efficiently than before. With the occasion of the anniversary of the failure, Richard Southword, the INTEGRAL Operations Manager, shares his impresions of one year of exciting operations.

INTEGRAL Conference 11-16 October 2021 updates: Registration is now open!

16 July 2021 it is now possible to register on line (no fee payment yet) and to send abstracts for oral and poster presentations for the INTEGRAL Conference, INTEGRAL: towards the third decade of X and Gamma ray observations. Also, using the direct link to the registration form.

Further details and updated information can be found at the Conference website.

INTEGRAL Conference: 11-16 October 2021

8 July 2021 We are pleased to confirm the next INTEGRAL Conference, INTEGRAL: towards the third decade of X and Gamma ray observations, which will be held in hybrid mode (i.e., an in-presence part and a broadcasted part via Zoom) at the Hotel Flamingo resort in Santa Margherita di Pula, Sardinia, Italy, on 11-16 October 2021. In this meeting we plan to review the most significant results obtained in 18 years of operation and lay out the new scientific goals achievable by exploiting INTEGRAL's heritage and capabilities. Further details (such as registration, abstract submission, etc.) will be communicated as soon as feasible.

INTEGRAL reloaded: spacecraft, instruments and ground system

24 June 2021 After more than 18 and a half years of operations, INTEGRAL is building an impressive legacy. A comprehensive update of the satellite status being in a harsh space environment, and an account of the successful Ground Segment will be published in New Astronomy Reviews. It will be part of a special issue dedicated to "15 years of INTEGRAL science". Get a sneak peek at


22 June 2021 The INTEGRAL AO-19 General Programme, as recommended by the Time Allocation Committee (TAC) and approved by ESA's Director of Science (Prof. Günther Hasinger), has been released and the observers have been informed. The programme can be found here.

INTEGRAL Conference postponed (again) to fall 2021

17 May 2021 The next INTEGRAL Conference, INTEGRAL: towards the third decade of X and Gamma ray observations, will now take place in October 2021, either in the week 11-16 or 17-22. The organizers have tentatively scheduled a hybrid conference with the in-presence part to be held in Sardinia and a broadcasted part via Zoom. However, due to the travel restriction unknowns, organizers are not in the conditions to confirm the in-presence part at the moment. Further details will be communicated as soon as feasible.

19th Announcement of Opportunity (AO-19): Preliminary submission statistics

19 April 2021 The deadline for the submission of proposals for AO-19 open time observations was on 9 April 2021, and all proposals are in the ISOC database. Below are some preliminary statistics on the proposals that have been received.

Total number of proposals
The total number of proposals received is 49. The total observing time requested is about 58 Msec (for all types of observation, i.e., fixed time, normal time, and ToO). Here, 10% of the requested total ToO time has been taken into account. Given that up to about 21 Msec of observing time (for new observing proposals) will be available for the AO-19 observing programme (12 months duration starting on 1 January 2021), this corresponds to an oversubscription in time by a factor of 2.8.

The non-ToO proposals are requesting data rights for 311 sources in total. 11 proposals requested joint time with NuSTAR, Swift and/or XMM-Newton.

Proposals per category
In the following table we give the breakdown of number of proposals as a function of the proposal category. Note that the numbers on requested observing times do include ToO proposals, but it has been assumed here, that a typical ToO proposal requests about 10% of its total observing time as entered into PGT from all the candidate sources included in a ToO proposal.

Scientific Category Number of proposals Requested observing time (Ms)
includes ToO times x 10%
Galactic Astronomy 25 43
Extragalactic Astronomy 15 7
Nucleosynthesis and diffuse
continuum/line emission
9 8
Total 49 58


Mid-May the Time Allocation Committee will peer review all proposals and recommend the AO-19 observing programme to ESA.


1 March 2021 Today, the ESA Director of Science (Prof. Guenther Hasinger) released the 19th Announcement of Opportunity (AO-19) for observing proposals with INTEGRAL.

This announcement solicits proposals for observations to be carried out from January 2022 for a period of 12 months. Proposers from all over the world are welcome to participate. All proposals will be subject to an independent peer review by the INTEGRAL Time Allocation Committee (TAC). The deadline for proposal submission is Friday 9 April 2021, 14:00 CEST.

More information can be found on the AO-19 page.

INTEGRAL: unravelling the mysteries of the X- and gamma-ray sky

27 January 2021 The INTEGRAL Project Scientist discussed with the Innovation News Network, some of the current and future INTEGRAL mission's activities, including studying flashes of powerful radiation that suddenly appear in the gamma-ray sky. The interview has been published in the online journal "The Innovation Platform Issue 4".

A gamma-ray burst from a magnetar in a nearby galaxy

15 January 2021 A mysterious gamma-ray burst that swept past the Earth on 15 April 2020, likely came from a magnetar in the nearby galaxy NGC 253. INTEGRAL helped establish the source of the burst. This finding confirms the long-held suspicions that some GRBs are in fact powerful flares from relatively close magnetars. See the NASA press release.

ISOC AO-18 observations underway and preparations for AO-19

4 January 2021 ISOC wishes you a healthy and successful 2021. The AO-18 cycle of observations started on January 1st and will last 12 months, see the INTEGRAL target lists and sky maps for details as well as the Long-Term Plan.

ISOC is preparing the next call for proposals requesting INTEGRAL observing time. The AO-19 release will be already on 1 March, with a deadline on 9 April 2021. The AO-19 cycle of observations is foreseen to begin on 1 January 2022 and has the usual duration of 12 months.

Release of AO-19: call for observing time proposals: 1 March 2021
Deadline for submission of observing time proposals: 9 April 2021 (14:00 CEST)
Meeting of the Time Allocation Committee: 18-20 May 2021
Start of AO-19 cycle of observations: 1 January 2022


News Archive