BEPICOLOMBO'S BEGINNING ENDS
A stunning early morning launch lifted the ESA/JAXA BepiColombo spacecraft into space on Saturday, 20 October. This marked the start of intensive, round-the-clock flight control activities to ensure the mission’s health and functioning in the harsh environment of space.
At 13:45CEST on Monday 22 October, just 58 hours into its mission, the critical first segment of the fledgeling satellite’s long voyage to Mercury was wrapped up, as teams at ESA’s mission control centre declared the critical ‘launch and early orbit phase’ complete.
The end of the beginning now beckons months of extensive in-orbit commissioning activities, in which operations teams will work extended hours daily until the end of December, performing tests to ensure the health of BepiColombo’s science instruments, its propulsion and other systems.
“Lots of people think you point a spacecraft in a particular direction and off it goes, making its own way to its final destination,” says Elsa Montagnon, Spacecraft Operations Manager for BepiColombo.
“In reality, the post-launch period is extremely busy, and so, too, is the long interplanetary cruise.”
“In the next months, teams on ground will be working in 12-hour shifts, including weekends, to get the spacecraft on the right path to the smallest planet of our Solar System.”
All systems GO
In the hours before Saturday’s liftoff, the Main Control Room of ESA’s ESOC operations centre was centre stage for the network countdown — a synchronised sequence involving facilities at ESOC, Europe’s Spaceport in Kourou, French Guiana, and at ground stations on four continents supporting the launch.
The final GO/NOGO rollcall saw Flight Director Andrea Accomazzo check in with the flight controllers at ESOC, each confirming they were “go for launch".
Shortly after, at 3:45 CEST on 20 October, BepiColombo hitched a ride into space on top of an Ariane 5 rocket, which provided a flawless orbit injection onto the planned interplanetary transfer trajectory.
Booster separation came just two minutes later, as the Ariane 5’s two solid rocket boosters detached themselves from the core stage; later, BepiColombo began its solo flight upon separation from the Ariane upper stage at around 4:12 CEST.
“Years of planning, and months of training and simulations led up to these fast-paced and vital moments,” recalls Elsa.
“Even after a successful liftoff and separation, we couldn’t relax. Everyone was waiting for the moment we heard BepiColombo’s first call, what we call the ‘Acquisition of Signal’.”
At 04:20 CEST, ESA’s deep space tracking station at New Norcia, Western Australia, picked up these first signals, followed by a rush of ‘telemetry’ — real-time status information and data — which was the first chance teams on the ground had to verify how the spacecraft was adapting to its new environment.
Next stop, Mercury
Since then, BepiColombo has not only communicated bundles of engineering telemetry, but its Mercury Transfer Module has also sent home spectacular images from a series of three low-resolution monitoring cameras, known as the “Selfie-cams.”
These images allowed flight controllers to visually verify the correct deployment of solar arrays and antennas.
Having worked around the clock since the launch of this remarkable mission, teams at ESA’s control centre in Germany are tired, but happy.
“The launch and early orbit phase was a huge success, but now comes seven years of complex operations as BepiColombo travels nine billion km to the innermost planet of the Solar System,” explains Paolo Ferri, Head of Mission Operations at ESA.
“The first ion thruster ‘operational arc’ will begin in mid-December, steering BepiColombo on its interplanetary trajectory.”
In an 'operational arc', the spacecraft's ion thruster runs at low energies for extended periods of hours and days, as opposed to traditional, high-energy chemical thruster burns that run for just minutes or hours. The benefit of an arc is it provides the same acceleration with less fuel mass.
Paolo continues, “With the combined experience from experts in operations, flight dynamics, mission data systems and deep space ground stations, BepiColombo could not be in more reliable hands.”
BEPICOLOMBO NOW FIRING ON ALL CYLINDERS
BepiColombo, the joint ESA/JAXA spacecraft on a mission to Mercury, is now firing its thrusters for the first time in flight.
On Sunday, BepiColombo carried out the first successful manoeuver using two of its four electric propulsion thrusters. After more than a week of testing which saw each thruster individually and meticulously put through its paces, the intrepid explorer is now one step closer to reaching the innermost planet of the Solar System.
BepiColombo left Earth on 20 October 2018, and after the first few critical days in space and the initial weeks of in-orbit commissioning, its Mercury Transfer Module (MTM) is now revving up the high-tech ion thrusters.
The most powerful and high-performance electric propulsion system ever flown, these electric blue thrusters had not been tested in space until now.
It is these glowing power-packs that will propel the two science orbiters – the Mercury Planetary Orbiter and Mercury Magnetospheric Orbiter – on the seven-year cruise to the least explored planet of the inner Solar System.
“Electric propulsion technology is very novel and extremely delicate,” explains Elsa Montagnon, Spacecraft Operations Manager for BepiColombo.
“This means BepiColombo’s four thrusters had to be thoroughly checked following the launch, by slowly turning each on, one by one, and closely monitoring their functioning and effect on the spacecraft.”
Testing took place during a unique window, in which BepiColombo remained in continuous view of ground-based antennas and communications between the spacecraft and those controlling it could be constantly maintained.
This was the only chance to check in detail the functioning of this fundamental part of the spacecraft, as when routine firing begins in mid-December, the position of the spacecraft will mean its antennas will not be pointing at Earth, making it less visible to operators at mission control.
The first fire
On 20 November at 11:33 UTC (12:33 CET), the first of BepiColombo’s thrusters entered Thrust Mode with a force of 75 mN (millinewtons). With this BepiColombo was firing in space for the very first time.
Three hours later, the newly awakened thruster was really put through its paces as commands from mission control directed it to go full throttle, ramping up to 125mN – equivalent to holding an AAA battery at sea level.
This may not sound like much, but this thruster was now working at the maximum thrust planned to be used during the life of the mission.
Thrust mode was maintained for five hours before BepiColombo transitioned back to Normal Mode. The entire time, ESA’s Malargüe antenna in Argentina was in communication with the now glowing blue spacecraft – the colour of the plasma generated by the thruster as it burned through the xenon propellant.
These steps were then repeated for each of the other three thrusters over the next days, having only a tiny effect on BepiColombo’s overall trajectory.
The small effects that were observed allowed the Flight Dynamics team to assess the thruster performance in precise detail: analysis of the first two firings reveals that the spacecraft was performing within 2% of its expected value. Analysis of the last two firings is ongoing.
Twenty-two arcs to go
“To see the thrusters working for the first time in space was an exciting moment and a big relief. BepiColombo’s seven year trip to Mercury will include 22 ion thrust arcs – and we absolutely need healthy and well performing thrusters for this long trip,” explains Paolo Ferri, ESA’s Head of Operations.
“Each thruster burn arc will last for extended periods of up to two months, providing the same acceleration from less fuel compared to traditional, high-energy chemical burns that last for minutes or hours.”
During each long-duration burn the engines do take eight hour pauses, once a week, to allow the ground to perform navigation measurements in quiet dynamic conditions.
The first routine electric propulsion thrust arc will begin in mid-December, steering BepiColombo on its interplanetary trajectory and optimising its orbit ahead of its swing-by of Earth in April 2020.
Travelling some nine billion kilometers in total, BepiColombo will take nine flybys at Earth, Venus and Mercury, looping around the Sun 18 times.
By late 2025 the transfer module’s work will be done: it will separate, allowing the two science orbiters to be captured by Mercury’s gravity, studying the planet and its environment, along with its interaction with the solar wind, from complementary orbits.
"We put our trust in the thrusters and they have not let us down. We are now on our way to Mercury with electro-mobility,” concludes Günther Hasinger, ESA Director of Science.
“This brings us an important step closer to unlocking the secrets of the mysterious innermost planet and ultimately, the formation of our Solar System.”
Follow ESA Operations on twitter for updates on BepiColombo’s journey, as well as the latest from ESA’s mission control.