The job of Integral, ESAs International Gamma-Ray Astrophysics Laboratory, is to collect the most energetic radiation that comes from area. The task of Integral, ESAs International Gamma-Ray Astrophysics Laboratory, is to identify and gather the most energetic radiation that comes from area. Since the least expensive point of Integrals orbit is now just 1500 km from Earths surface, the spacecraft passes through both radiation belts in its orbit.
The first obstacle was to decrease Integrals energy consumption to buy more time. Only the very energetic gamma rays can leave and be detected by Integral.
The job of Integral, ESAs International Gamma-Ray Astrophysics Laboratory, is to collect the most energetic radiation that originates from area. Credit: ESA. Illustration by D. Ducros
On September 22, around midday, ESAs Integral spacecraft went into emergency Safe Mode. Among the spacecrafts 3 active reaction wheels had shut off without caution and stopped spinning, causing a ripple impact that indicated the satellite itself started to rotate.
As a result of the spacecraft turning, data were just reaching ground control patchily and the batteries were rapidly discharging. With simply a few hours of power left, it appeared possible that the 19-year-old mission could be lost.
The task of Integral, ESAs International Gamma-Ray Astrophysics Laboratory, is to find and collect the most energetic radiation that comes from space. The spacecraft was introduced in October 2002 and is assisting resolve some of the biggest mysteries in astronomy. Credit: ESA/D. Ducros
The Integral Flight Control Team, together with Flight Dynamics and Ground Station Teams at ESAs ESOC objective control, teams at ESAC and Airbus Defence & & Space, set to work. With quick thinking and innovative options, they found the problem and rescued the objective.
What on Earth?
A Single Event Upset (SEU) happens when a charged particle strikes a sensitive part of electrical devices, causing a one-off modification of state that interrupts its functioning. These charged, ionized particles typically come from the Sun when it spews out matter and energy throughout solar flares or coronal mass ejections.
Three hours to save Integral– what occurred? Credit: ESA
” I do not think that the SEU on this celebration was caused by our regional, periodically irritated star. This strike happened on a day when no relevant space weather condition activity was observed,” describes Juha-Pekka Luntama, ESAs Head of Space Weather.
” Based on a discussion with our colleagues in the Flight Control Team, it appears like that the anomaly was set off by charged particles caught in the radiation belts around Earth.”
The Van Allen radiation belts are 2 doughnut-shaped regions encircling Earth, where energetic charged particles are trapped inside Earths magnetic field. Their residential or commercial properties differ according to solar activity and they represent a hazard to satellites and humans in space that pass through them. Because the lowest point of Integrals orbit is now just 1500 km from Earths surface, the spacecraft goes through both radiation belts in its orbit.
Darmstadt, we have an issue
Essential usages response wheels– wheels that keep energy as they spin– to subtly control the direction the spacecraft points in without the requirement of thrusters.
All of a sudden, among these reaction wheels stopped and, due to the fact that of the law of conservation of energy, that turning force formerly in the wheel needed to go someplace else– the entire spacecraft. The spacecraft began to spin, activating an Emergency Safe Attitude Mode which sadly, due to a previous failure, was no longer reputable and did not manage to support the objective.
The Integral Flight Control Team set to work saving the mission. Credit: ESA
The reaction wheel was reactivated by teams on the ground, but the spacecraft kept spinning at an average rate of about 17 degrees per minute (roughly one rotation every 21 minutes), as well as wobbling unexpectedly about its axes. This may not seem like much, but the spacecraft was rotating at 5 times its maximum when under control.
” The information coming down from Integral was choppy, coming in for short periods due to it spinning. This made analysis even harder,” explains Richard Southworth, Operations Manager for the objective.
” The batteries were releasing, as there were only brief charging durations when the panels quickly faced the Sun.”
The first difficulty was to reduce Integrals energy consumption to buy more time. Price quotes of the charge remaining prior to blackout and the loss of the satellite was just 3 hours. Step by step, by switching off non-critical parts and various instruments, this increased to more than six hours. Next action– stop the spinning.
With assistance from industry professionals, the group at ESOC evaluated the state of the response wheels, creating a series of commands to alter their speed and brake the spinning satellite. By late afternoon, the commands were sent and immediately showed success, but another three long hours passed before the satellite was totally under control and out of immediate threat.
Integrals Apollo 13 minute
” Everyone breathed a big sigh of relief. This was very close, and we were tremendously relieved to get the spacecraft out of this near-death experience,” recalls Andreas Rudolph, Head of the Astronomy Missions Division in ESOCs Mission Operations Department.
” Most of the Control Team were working from home at this point– I was following operations from the train!– and worked until four in the early morning to get the spacecraft totally stable, back into position and dealing with the Sun to charge its batteries.”
The remaining gas surrounding the black hole forms a thick cloud that obstructs most of the radiation. Just the very energetic gamma rays can be and get away spotted by Integral. Credit: ESA
Regrettably, a couple of hours later on as the group reconvened to talk about the next actions, the spacecraft as soon as again began to rotate, its reaction wheels once again turning at high speed. The factor for this is still not completely understood but is thought to be related to a star tracker occultation or blinding which wasnt managed correctly by the satellites control systems– effectively when Earth gets in the way of the spacecrafts view of the stars, which it utilizes to orient itself.
The group repeated the previous days actions to stabilize the spacecraft and go back to a Sun pointing position, this time without getting in the method of the star trackers. The recovery took simply a couple of hours, implementing the lessons found out from the first time.
Hubbles sharpest view of the Orion Nebula. This remarkable image offers a peek inside a cavern of dust and gas where thousands of stars are forming. The image, taken by the Advanced Camera for Surveys (ACS) aboard NASAs Hubble Space Telescope, represents the sharpest view ever taken of this area, called the Orion Nebula. More than 3000 stars of numerous sizes appear in this image. Some of them have never ever been seen in noticeable light. Credit: NASA, ESA, M. Robberto (STScI/ESA) and the Hubble Space Telescope Orion Treasury Project Team
Essential has because stayed under control, and from September 27 all systems are back online. Given that October 1, after an extended checkout, its instruments are back observing the high energy Universe.
One of the first targets for Integral will be to observe enormous stars in the Orion region, and study the effect on their environments when they go supernova.
” We are also back to target of opportunity observations, which implies that Integral is again reacting rapidly to study unforeseen explosive events in deep space,” states Erik Kuulkers, ESAs Project Scientist for Integral.
Artists view of Integral. Credit: ESA
An issue of thrust
Its not the very first time this nearly 20-year-old mission gave the control team at ESAs ESOC Operations Centre a scare. Last year, Integral fired its thrusters for possibly the last planned time, after a failure with its propulsion system.
Its this lacking propulsion system that implied a normally remedying Safe Mode was inadequate on this occasion. With the mode now disabled, the Control Team are dealing with a new automatic rescue series that ought to simulate a lot of the operations performed after this abnormality, only much quicker.
When the propulsion system failed, the group recognized they would need to discover to maneuver the four-tonne satellite utilizing its highly delicate response wheels alone, to dump energy at routine durations and counteract forces on the spacecraft, including the mild shove from the Suns light. It was a solution that had never been tried before.
” I didnt believe it was possible in the beginning. We examined with our flight dynamics coworkers and the theory indicated it would work. After doing a simulation, we tested it on the spacecraft. It worked,” describes Richard.
” Thanks to our quick-witted group and the assistance of experts from throughout market, Integral lives on. Almost 20 years old, it is far outliving expectations for what was indicated to be a five-year objective.”
Listen to Richard recount the story of Integrals previous rescue and upgrade and the incredible teamwork that conserved the objective, in the most recent episode of the ESA Explores Space Operations podcast.