ESA’s Solar Orbiter Swings past Earth this week • The Register

Interview ESA’s Solar Orbiter must fly past Earth, requiring careful waste assessment as it dives close to the International Space Station (ISS) orbit ahead of its main scientific mission.

The overflight is to take place on 26 and 27 November.

The amount of waste in orbit was usefully increased last week by Russia’s anti-satellite missile demonstration, much to the dismay of NASA and other space organizations.

With the Solar Orbiter set to pass over North Africa and the Canary Islands as it approaches November 27, it must make it through two areas of potential space debris; geostationary orbit and low earth orbit.

“At 12 km / s, we would be a really effective ASAT weapon,” says Daniel Lakey, Solar Orbiter spacecraft operations engineer at ESA. Reg, referring to the speed at which the spacecraft will barrel forward.

The team has already assessed whether the first Trajectory Correction Maneuver (TCM) – or “TCM-3d” in spacecraft operations speaks – needed adjustment. The good news was that it did not do so after Tuesday’s meeting.

The “standard” guidance profile was executed as planned instead, “he says.

The first TCM window (aka TCM-6h) will occur just before midnight on November 26, when the spacecraft will be only six hours from its nearest approach to Earth.

“For TCM-6h, FD [Flight Dynamics] “will calculate a number of alternative orbits that will be monitored by ESA’s Space Debris Office against known objects that will report back on the likelihood of a collision,” Lakey said.

Hopefully everything will go well, despite the increasing amount of dirt around the Earth, and an adjustment will not be necessary. As for what would trigger a moment with all hands to the pumps, “2 * 10-5 for TCM-6h, “he says.” If there is a greater likelihood of a collision, a CAM must [Collision Avoidance Maneouvre] A lane with a lower chance of a collision and the lowest delta V requirement will be chosen. “

If a change is needed to adjust the course, the team will only have a matter of hours to put together the instructions and get them aboard the Solar Orbiter. That’s, Lakey says, “about the fastest turn we can make.”

“Because we always have a complete ‘chain’ of attitude guidance for spacecraft on board, we have to juggle the new commands to make sure they do not collide with the old ones or end up with none at all,” he says. “Both equally bad.”

The orbit was plotted years ago, and this bypass is required to reduce the spacecraft’s energy prior to its next closest observation of the Sun.

In Deep Space, waste is not something the team is so worried about, but now it has jumped to the top of the agenda. ESA has plenty of experience avoiding waste, although Lakey points out: “Unlike our friends next door in the Earth Observation Division, things are complicated for us because of the inherent uncertainties in our orbit and the time required for to process the tracking data. “

“Although they no doubt wonder why we make so much fuss about making a CAM as they do them with some regularity these days,” he adds.

And the infamous missiles in orbit? “Whereas our colleagues in the SDO [Space Debris Office] have not had their lives made easier by the ASAT test, it does not change our plan – we are a bit on rails at this point and will hurry past Earth at an altitude of about 450 km at. 04:30 on the 27th, come what may. “

ESA’s own figures indicate the altitude to 460 km, to which Lakey says: “Flight Dynamics would be able to give an expected value within a large number of decimals, but it would be in relation to the center of the earth …”

As for the spacecraft itself, it remains in good health. The team is running well below the fuel budget, but if it proves necessary to adjust delta-V, that margin will start to be eaten into. That said, the budget should not be exceeded, “but in the end yes, the less we fire off the thrusters, the less fuel we use.”

The instruments all gather on science, and the spacecraft is due to dive down to 0.32AU in March. The heat shield has also worked well, “to the point we’ve developed a ‘defrost maneuver’ to heat the back of the spacecraft,” Lakey says. “Mooning the Sun, if you will.”

In fact, the mission is packed full of unknowns for ESA, and Lakey tells us, “there’s a lot to learn about how to fly a spacecraft there.”

The hope is that the mission will be extended. After all, ESA’s Mars Express is 18 years old inside a two-year mission (launched in 2003, it was only intended to operate for two years. The mission was recently extended to the end of 2022). This assumes that the Solar Orbiter does not hit anything when it passes the Earth.

The team will be at the European Space Operations Center and “see telemetry as hawks,” Lakey says. “We are used to being hundreds of millions of miles away from Earth with long signal propagation delays, so it’s pretty new for us to see the data come down in real time.”

“If we had hatches, we would knock them down now.”

And if the worst were to happen? “I do not think humanity has created any structure that would withstand a waste dump at the speeds we drive.”

“I prefer not to think too much about it.” ®

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