INTEGRAL News archive for 2020



Happy 18th birthday, INTEGRAL!

17 Oct 2020  On this date, 18 years ago, INTEGRAL was launched at 01:33 UTC with a Proton rocket from Baikonur, Kazakhstan. INTEGRAL is still operating successfully, and continues to explore the most energetic radiation that comes from space. It is an ESA mission in cooperation with Russia and the United States.

Extended operations confirmed for science missions, including INTEGRAL

13 October 2020  It was announced today that all ten missions, including INTEGRAL, that got an indicative extension in 2018 were approved by the SPC for operations in 2021 and 2022. The decision was taken during the SPC meeting held on 1 October and follows a comprehensive review of the scientific merits and technical status of the missions.

In principle, Mars Express, Cluster and INTEGRAL will need to prepare for an end of operations by Dec 2022. However, at the same time, ESA would like to engage in a creative process for these missions and develop innovative concepts that could be presented, e.g., at the June 2021 SPC meeting and would make it attractive for the SPC to re-evaluate their decision.

OSA 11.1 Release

22 September 2020  ISDC released OSA version 11.1 which is available with updated documentation at the ISDC website at the links


  • Added binary distribution for Ubuntu 20.04.
  • Corrected compatibility issue with Heasoft 6.26 which prevented the rebinning of response matrices for ISGRI and JEM-X.
  • Upgraded ii_light, lc_pick, ibis_isgr_energy, and j_ima_iros.
  • Updated installation guide and IBIS user manual.
  • Improved script 


INTEGRAL resumes ToO observations

5 August 2020  It is with great pleasure that we can announce that INTEGRAL is accepting once again requests for Target of Opportunity (TOO) observations. Proposers are welcome to submit their requests for both accepted as well as new TOOs through the usual channel ( As is always the case, implementation will be considered on a case by case basis.

Following a reaction wheel bias (RWB) that caused a large drop in pressure in the attitude control fuel system on 17 July 2020, much thinking, discussion, and effort have been invested in developing a safe new way of performing spacecraft attitude control that does not require RWBs. The teams at MOC and ISOC have been able to implement a scheduling strategy that minimises the accumulation of angular momentum even more efficiently than previously with the goal of making operations entirely free from the need for RWBs. 

This new strategy involves spending approximately half the observing time pointing to opposite directions in the sky in order to cancel out as much as possible the accumulation of angular momentum caused by the radiation pressure on the solar panels. The strategy is also applied during the time that the spacecraft is within the Earth's radiation belts by selecting an optimal perigee passage attitude. This new approach, referred to as the Z-flip strategy in reference to the reversal of the pointing axis, will require further software and procedural updates whose implementation has already begun. 

INTEGRAL helps unravel origin of Fast Radio Bursts

28 July 2020  A global collaboration of telescopes, including INTEGRAL, has detected a unique mix of radiation bursting from a dead star in our galaxy — something that has never been seen before in this type of star, and may solve a long-standing cosmic mystery. See ESA/Science & Exploration/Space Science News.

INTEGRAL resumes Science Operations

8 July 2020  After the temporary interruption of science operations to allow for further system tests (see News Item from 23 June 2020), the return to science observations had taken place as planned in revolution 2244, starting 25 June. Mission planning is currently optimized such that Reaction Wheel Bias (RWB) dumps are delayed as much as possible. Still, a necessary RWB under thruster control that took place on 3 July was executed nominally and fully autonomously without human intervention, and with no associated drop in the Reaction Control System (RCS) pressure. ISOC and MOC teams are on a steep learning curve gaining experience in the new way of operating INTEGRAL.

INTEGRAL AO-18 General Programme Approved

6 July 2020  The INTEGRAL AO-18 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. It can be found here.

INTEGRAL scientific operations have temporarily been interrupted

23 June 2020  The INTEGRAL mission operations team found that after a reaction wheel bias (RWB) to offload momentum, the pressure in the tanks had dropped by a few tenth of a bar, which then only slowly recovered. In order to further investigate the behaviour of the INTEGRAL system recovery after a RWB coinciding with propellant system pressure drop, and as a test to check a possible new operational approach delaying RWB momentum dumps and thruster usage, scientific operations have temporarily been interrupted in revolution 2243 (that started on the evening of June 22). Pending on the outcome of the test, the plan is to return to science observations in revolution 2244, starting 25 June. Further tests eventually impacting on science performance may be necessary in the future.

ESA Proposal to SPC for Extensions of mission operations for the period 2021 - 2025

23 June 2020  Find below information on the ESA inputs to the SPC meeting #163, planned for July 7-8, deciding about extensions of mission operations for the period 2021-2025 (2 years confirmation + 3 years extension):

Like all the other science missions in operations, also INTEGRAL had received positive reviews and recommendations on the extended mission science case from the Astronomy Working Group (AWG) and the Space Science Advisory Committee (SSAC) that met the 1st half of June.

In light, however, of the need to resolve broader programmatic and cost issues the ESA Directorate of Science Programme is facing in this and the coming 2 years, the Executive decided to postpone a proposal on the extension of the operations of Cluster, INTEGRAL and Mars Express to the next SPC meeting (#164, planned for November 2020).

INTEGRAL Conference 2020 postponed to 2021

19 June 2020  Due to the COVID-19 pandemic, the INTEGRAL conference 2020 "towards the third decade of X and Gamma ray observations" has been moved to 24-29 May 2021. Venue, title, and other aspects communicated so far are unchanged. For details, see the website:

INTEGRAL's return to science after the 8th Emergency Safe Attitude Mode

Update 12 June 2020  We are pleased to inform that science operations have been resumed as of today. They still require manual intervention at various steps, but it seems that INTEGRAL will be at 95% observing efficiency. A great achievement, within a month after the anomaly.

In the meantime, work is continuing to automate operations to allow a return to close to full scientific observatory utilisation in the mid term (expected is end July); in parallel, investigations are ongoing to understand and characterise the failure case.

5 June 2020   Emergency Safe Attitude Mode (ESAM, the 8th case since launch) was triggered on 16 May 2020 during thruster firing for a standard Reaction Wheel momentum dump. While in the stable Sun pointing safe mode under redundant thruster attitude control, a significant de-pointing took place, automatically recovered within minutes.

The analysis of safe-mode entry and subsequent de-pointing together with dedicated thruster calibrations of both the standard and redundant Reaction Control Systems (comprising of tanks, fuel pipes and thrusters) showed that INTEGRAL experienced a reduction in pressure (from 5.5 to ~5 bar) in the propellant system; thrusters on both chains are found to be underperforming since then at ~50% level with irregular thrust levels. Under the supervision of an Anomaly Review Board, including experts from ESOC (Flight Control and Flight Dynamics Teams) supported by ESTEC (TEC: Propulsion) and Industry (Airbus & Thales), activities are ongoing to study the possible root cause of the anomaly and characterise the changed behaviour, focusing also on remaining fuel and tank pressurant, avoidance of future ESAM entry, and an operational strategy for the handling of the Reaction Wheel control.

Additionally, high priority is now being given to the return to science operations: as the spacecraft observing mode is operative, the science instruments collecting data in staring mode and thrusters performing (they can do so down to at least 3.5 bar according to specs), re-enabling full science observations including the implementation of Targets of Opportunity is targeted by end July.

A modified strategy for alternative wheel control has already successfully been validated. In the early phase of the return to science from mid June, this approach will be based on manual wheel speed adjustments, performed and monitored manually during working hours, including weekends, with a somewhat reduced observing efficiency (~80% TBC). Planning files will need to be modified, tested and handled by the mission planning software at MOC and SOC, which may require some (modest) modifications. As this innovative strategy is expected to leave observing constraints unchanged, the plan is to resume nominal scheduling of the AO-17 Guest Observer program, as originally foreseen.

The full deployment of this new strategy, including in the end again an automated execution of wheel biases, has been kicked-off and is currently pending on necessary changes in mission planning and control software, databases and procedures, on testing progress, and training of Spacecraft Controllers and on-call teams. Full functionality is thus hoped to be restored by end July.

INTEGRAL recovery from Emergency Safe Attitude Mode (ESAM)

Update 28 May 2020  The Thruster Torque calibration with RCS-A was successfully performed on 25 May, showing similar reaction control thruster performance as RCS-B: all thruster are now confirmed to be working and full redundancy in RCS has been re-established.

All thrusters are showing significantly reduced and less stable performance, a behaviour linked most likely to reduced pressure in the propulsion system; a pressure drop from 5.5 to about 5.0 bar had been experienced during the de-pointing on 17 May. Investigations on the root-cause of the pressure drop are on-going. One (TBC) hypothesis being that nitrogen gas, used as tanks pressurant, might have formed bubbles in the hydrazine fluid propellant system that could have been leaving the propulsion system, interrupting thruster firing and explaining the pressure loss. Thrusters are qualified to continue working at least down to 3.5 bar, albeit with decreasing performance.

Instruments (IBIS, JEM-X, SPI) are observing in staring mode, i.e. without spacecraft slews (OMC in Safe Mode due to the attitude). Targets of Opportunities can currently not be performed. The spacecraft remains in stable attitude under reaction wheel control. Another reaction wheel momentum off-loading is planned to be performed on 29 May.

Further discussions on resuming science operations are on-going, including plannings for a modified wheel speed handling procedure.

Update 25 May 2020  In order to prevent reaction wheel 2 or 4 reaching the maximum wheel speed and to avoid autonomous momentum dumping with unpredictable results, on 22 May at 10:00 UT an adjustment of the INTEGRAL wheel speeds was performed: A series of small wheel speed changes was commanded to approach slowly and step by step the desired wheel speeds, limiting the impacts on the satellite inertia moment such that they could easily be absorbed by the thrusters, even with the currently observed reduced thruster performance.

The operation was entirely successful and the spacecraft behaviour as predicted when planning the operation, giving more than 1 weeks time before the need to adjust the wheels speed again, marking also an important first step in demonstrating that INTEGRAL remains controllable in a predictable way.

Investigations about the root cause of the anomaly are still on-going, including further evaluation of the health and performance of the Reaction Control Subsystem (RCS).

A Thruster Torque calibration with RCS-A will start at 15.00 today.

19 May 2020  On 16 May 2020 at 15:30 UT, during a Reaction Wheel Bias (RWB) and triggered by a Pitch Thruster Impulse Monitoring (1) anomaly, INTEGRAL entered nominally into Emergency Safe Attitude Mode (ESAM), turning the spacecraft into an attitude position allowing optimum Solar array power production (Sunline), and putting the payload into a safe configuration.

At 06:30 UT on 17 May, a number of out-of-limits were noted on the payload units, corresponding to an unscheduled eclipse passage, putting the instruments into 'eclipse mode'. Attitude sensor data showed a significant de-pointing, i.e., INTEGRAL had moved quickly away from the Sunline before re-pointing back to the expected Sun pointing direction under thruster control. The reason for this anomalous behaviour during ESAM is at this time not yet understood.

As the thrusters might be related to the cause of the satellite control anomaly, the pressure to move out of thruster-controlled ESAM mode received highest priority. The spacecraft needed to be placed back into Inertial Pointing and Slew (IPS) mode stable under reaction wheel control. The INTEGRAL Flight-Control and Flight-Dynamics teams managed (working almost completely remotely) to achieve IPS mode during the evening of 17 May. Payload reconfiguration after the unexpected 'eclipse' continued afterwards and the expected configuration was reached later in the night. Thruster behaviour was nominal during this operation. Reaction wheels were spun up to 100 RPM each. As the ESAM exit attitude was unconstrained until 19 May at 04:00 UT, a slew to a different safe attitude position took place that will be unconstrained at least until 24 May, adding additional time to continue investigating the causes and recovery scenarios, before the next required manoeuvre.

Regular Anomaly Report Meetings are taking place to define next actions with high urgency, and actions for investigation, including an inventory of all possible theoretical root causes for the ESAM trigger and de-pointing.

No science operations can be performed for the time being. Further updates will be communicated in due time.


(1) The Pitch Thruster Impulse Monitoring (PTIM) anomaly detection monitors the change in effective angular momentum on the spacecraft Pitch Axis by accumulating the sum of the on-times of Thrusters T1 & T4 minus the on-times of Thrusters T2 & T3.

18th Announcement of Opportunity (AO-18): Preliminary submission statistics

14 May 2020  The deadline for the submission of proposals for AO-18 open time observations was on 4 May 2020, 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 52. The total observing time requested is about 70 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-18 observing programme (12 months duration starting on 1 January 2021), this corresponds to an oversubscription in time by a factor of 3.35.

The non-ToO proposals are requesting data rights for 336 sources in total. 14 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 29 55
Extragalactic Astronomy 12 4
Nucleosynthesis and diffuse
continuum/line emission
11 11
Total 52 70


Near the end of June, the Time Allocation Committee will peer review all proposals and recommend the AO-18 observing programme to ESA.

Update: Coronavirus & INTEGRAL Conference

30 April 2020  Due to the known events regarding the COVID-19 situation, the final dates of the INTEGRAL Conference, "INTEGRAL: Towards the third decade of X- and Gamma-ray observations", to be held 5-10 October 2020 in Sardinia, Italy, will be confirmed at the end of May. Apologies for any inconvenience this may cause. Contact the organizers at integral2020 (at) for further information.

INTEGRAL AO-18 proposal submission deadline delayed to 4 May 14:00 CEST due to COVID-19, coronavirus

23 March 2020  ESA is doing its best to guarantee that the proposal submission and review processes remain optimal within the restrictions imposed by the COVID-19, coronavirus crisis. Since measures deployed in the ESA’s Member States have disrupted scientific activities in those countries, the INTEGRAL AO-18 proposal submission deadline has been postponed from Friday, 3 April to Monday, 4 May 14:00 CEST.


2 March 2020  Today, the Director of Science (Prof. Guenther Hasinger) has released the 18th Announcement of Opportunity (AO-18) for observing proposals with INTEGRAL.

This announcement solicits proposals for observations to be carried out from January 2021 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 3 April 2020, 14:00 CEST.

More information can be found on the AO-18 page.