Spacecraft fall silent as Mars disappears behind the Sun

Enabling & Assist

17/11/2023
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The area between Earth and Mars is often buzzing with science information, telemetry and instructions racing to and from virtually a dozen missions on the Purple Planet. However for roughly one and a half days this November, communication between the planets will fall silent as Mars passes behind the Solar.

Tis the season for conjunction

Through the conjunction season, the Solar’s corona interferes with the radio alerts used to speak with missions at Mars.

Photo voltaic conjunction for Mars happens roughly as soon as each 25 months. Throughout conjunction, Mars is situated on the alternative aspect of the Solar from Earth.

Across the time of conjunction, the radio alerts used to ship instructions from Earth to the spacecraft and to obtain alerts from the spacecraft will be disturbed by the Solar’s lively environment – the photo voltaic corona.

The time frame throughout which communications are considerably disturbed depends upon the dimensions and energy of a Mars spacecraft’s communication gear, however sometimes takes place whereas the angle within the sky between the Solar and Mars as seen from Earth is inside 3–4°.

In 2023, this era lasts from early November to early December.

Mars considered from Earth throughout photo voltaic conjunction

On account of the disruption, mission controllers can’t reliably ship instructions to, or obtain information from their spacecraft. Particular precautions should be taken.

For ESA’s Mars Categorical and ExoMars Hint Gasoline Orbiter (generally known as MEX and TGO, as a result of we take pleasure in our acronyms), this implies ‘uplinking’ all of the vital directions the spacecraft would wish to function with none contact from Earth for the complete interval. That’s three or 4 weeks of instructions once we usually ship up just one week at a time.

In fact, these conjunctions additionally have an effect on the missions of different area companies – and this sort of factor isn’t distinctive to Mars.

Floor stations to full energy!

As a result of disturbance from the Solar’s environment throughout conjunction season, we’ve got to scale back the quantity of knowledge we alternate with MEX and TGO.

We minimize the quantity of knowledge that we ‘uplink’ to MEX, for instance, down from 2000 bits per second to simply 250 and cut back the quantity of knowledge that MEX sends right down to Earth to as little as 300 bits per second.

We additionally set our Estrack floor stations to most transmission energy to verify our spacecraft hears us loud and clear regardless of the disturbance, i.e., we use a louder voice however say fewer phrases.

This limits the sort of data that MEX can ship to its operators on Earth to ‘housekeeping’ information – well being standing and telemetry – and is just too low for MEX to ship any science information.

Like a diver holding their breath, any information gathered by MEX’s devices in the course of the conjunction interval should be saved within the restricted onboard reminiscence till the season is over.

ESA’s New Norcia deep area antenna in communication with Mars Categorical close to the beginning of the 2023 Mars photo voltaic conjunction season. At 300 bits per second, this GIF would take over three hours to obtain.

What makes the 2023 conjunction particular?

20 years and counting: Mars Categorical in numbers

Mars Categorical arrived on the Purple Planet on 25 December 2003 and is considered one of Europe’s longest-serving missions. The staff celebrated 20 years since launch this summer time with the first-ever stay webcast from one other planet.

This will probably be MEX’s tenth photo voltaic conjunction and TGO’s third. Nonetheless, because the orbits of Mars and Earth have barely completely different inclinations, Mars doesn’t often go straight behind the Solar.

The orbits of Earth and Mars in the course of the 2023 photo voltaic conjunction

The 2023 conjunction is uncommon in that it will likely be the primary time that Mars passes behind the disc of the Solar for the reason that two ESA spacecraft arrived.

Whereas Mars is behind the Solar, for roughly one and a half days on 17–18 November, communication with MEX and TGO received’t simply be restricted, it’ll be unimaginable. 

These home windows of restricted or unimaginable communication between Earth and Mars will pose a problem for future human settlers, too.

Are you apprehensive?

Mars in the course of the 2023 photo voltaic conjunction

“Originally of the mission, the staff was very cautious about conjunctions,” says James Godfrey, Spacecraft Operations Supervisor for Mars Categorical. “If one thing goes severely flawed in the course of the conjunction interval, it might be tough to get better the spacecraft till it’s over.”

“We used to droop all science operations. However, over time, we’ve solely ever skilled minor disruptions.”

“In 2019, we found that we are able to proceed utilizing a few of MEX’s devices in a restricted approach, so long as all instructions are uploaded earlier than the season begins, and all science information are saved on board till the season ends.”

“Initially, planning for conjunctions was a really handbook course of,” says James Godfrey. “However over time, it’s develop into largely routine.”

Peter Schmitz, Spacecraft Operations Supervisor for Hint Gasoline Orbiter, provides: “With its bigger communications antenna and information storage capability, TGO is ready to proceed with its information relay actions for Mars floor property all through the conjunction interval – even when Mars is straight behind the Solar – and put together to downlink all the saved information to Earth when it’s as soon as once more secure to take action.”

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