Space Sunday: ISS, a lunar time zone and an aurora

Russia’s uncrewed Soyuz MS-23 launched for the International space station on February 24th, 2023, on its way to replace the Soyuz MS-22 vehicle struck by a major coolant leak in December 2022, leaving it incapable of returning crew members Sergey Prokopyev, Dmitri Petelin and Frank Rubio to Earth as planned at the end of their 6-month rotation.

Due to the lack of any return capability, NASA and Roscosmos had worked on an emergency scenario whereby the Soyuz seat for Rubio had been transferred to Crew Dragon Endurance to allow his return with the 4-person members of NASA’s Crew 5 in the event of an emergency evacuation being called for ahead of MS-23’s arrival; the theory being that this would reduce the heat load in the Soyuz return capsule, allowing Prokopyev and Petelin to survive a return to Earth in that vehicle.

Having arrived at the ISS on February 25th, the crew started work in off-loading the ~430 kg of cargo MS-23 carried to the ISS and then moving the flight seats for the MS-22 crew into the newly-arrived Soyuz. It is not clear when MS-22 will be undocked from the ISS to attempt an automated return to Earth; however, its crew will now spend almost a year in space, as MS-23 will not make a return to Earth until September 2023, giving Roscosmos time to completely reshuffle crew rotations.

In the meantime, NASA’s Crew 6 mission launched from Kennedy Space Centre on March 2nd, aboard SpaceX Crew Dragon Endeavour delivering NASA astronauts Stephen Bowen and Warren Hoburg, cosmonaut Andrey Fedyaev and Emirati astronaut Sultan Alneyadi to the space station on March 3rd, after a one-hour delay in docking whilst a faulty sensor on the docking system was corrected.

Bowen is due to take over the role of ISS commander from Prokopyev, marking the start of NASA Crew Rotation 69. Following handover, the Crew 5 mission, comprising NASA astronauts Nicola Mann and Josh Cassada, together with JAXA astronaut Koichi Wakata and cosmonaut Anna Kikina (the first Russian to fly a US commercial crew programme flight, and the first Russian to fly on a US spacecraft since 2002) will depart the ISS aboard Endurance for Earth, possibly around March 8th.

Crew 6 almost marks the last flight of Crew Dragon under the initial contract between NASA and SpaceX which pegged launch fees at US $220 million / US$55 million per seat.  From the August Crew 7 launch through until Crew 14 (~2028), SpaceX Crew Dragon flights will average US $288 million / US $72 million per seat.

Giving the Moon its Own Time Zone

A human return to the Moon and the potential for establishing a permanent presence there involves many things. Most of the time, efforts are focused on the technologies required: launch and landing systems, communications system, life support, etc. However, one thing people likely do not consider is the matter of how time will be kept.

Until now, missions to the Moon have operated on a time frame based on their country of origin, with their onboard chronometers synchronised with terrestrial time. However, this will not work going forward, when there will be multiple missions – crewed and robotic – operating on and around the Moon.

To facilitate these missions, NASA and the European Space Agency (ESA) are developing new orbital services such as the Lunar Communications Relay and Navigation System and Moonlight, both of which might be thought of a combination of communications as GPS data services such as the US GPS and European Galileo systems.

The latter have their own timing systems, but they possess offsets relative to one another of just a few billionths of a second, allowing them to operate on concert. In particular, they are fixed to the Universal Coordinated Time (UTC) global standard, which is also used by the internet and aviation, as well as scientific experiments that require highly precise time measurements. This allows both networks to remain fully in synch with one another and with ground-based units.

Having a universal time standard for the Moon and cislunar space is important because clocks run slower on the Moon’s surface than on Earth by 56 millionths of a second per terrestrial day, whilst clocks placed in different orbits around the Moon will run at different rates to one another and those on the lunar surface. Over time, this can result in communications and data errors to be introduced, so having a singular reference point – time zone – unique to lunar operations is essential for such time-keeping and allowing for things like accurate navigation across the surface of the Moon and when in orbit around it.

To this end, and following meetings hosted by ESTEC, the European Space Research and Technology Centre, space organisations such as NASA, ESA and JAXA, have agreed to develop LunaNet. Based on the core concepts of GPS and Galileo, LunaNet is intended to provide a set of mutually agreed-upon standards, protocols and interface requirements for inter-operability between multiple space and surface units operating around on the Moon, all utilising the same time standard.

Exactly how this standard will be defined and will be responsible for maintaining it or what it should be called has yet to be determined. UTC, for example, is not maintained by any one nation, but by the intergovernmental International Bureau of Weights and Measures (IBWN) based in Paris, France. One suggested name for the new time zone is “selenocentric reference frame” (SRF), which doesn’t exactly roll off the tongue. It has also yet to be decided whether or not it should be synchronised with time zone on Earth. However, as a necessary requirement, developing and defining it could help with future deep-space missions.

UK Treated to Almost Nationwide Auroral Display

On February 24th and again of February 25th, the Sun gave off a pair of coronal mass ejections (CMEs) – massive eruptions of material throwing billions of tonnes of energetic material from the corona and free of the Sun’s gravity well. CMEs are a common event and can move in any direction relative to the Sun. As it so happened, this pair fired Earthward, travelling at around 3 million km/h, each arriving at a time when they were ideal viewing in the evening skies over the UK.

After a journey of 150 million km, the material from the first CME slammed into the Earth’s magnetosphere over an UK just settling down for a quiet evening under clear skies on Sunday, February 26th. The result was a sizeable geomagnetic storm in which electrons in the magnetosphere were accelerated into the atmosphere by the blunt force of the CME material, sparking intense auroral displays which rapidly spread far further south than is usually the case, giving people across Britain with a glorious display.

Twenty-four hours later, the second CME struck, this time coinciding with lunchtime in the UK and largely overcast skies. However, such was the nature of the resultant geomagnetic disturbance, coming hard on the heels of the first, resulted in a second extensive auroral display which was still visible  in the evening across many parts of the UK as the skies darkened – and the weather cleared again.

Rocket Lab Considering Sea-Based Rocket Recovery

Rocket Lab, the small satellite launch company based in New Zealand and the US  is reconsidering its plans for dramatic aerial captures of the first stage of its Electron rocket in favour of at-sea recoveries.

The company came up with the novel idea of trying to “hook” the 12 metre tall, 1.2 metre wide booster out of the air as it descended back to Earth under parachute on the ground that keeping it out of the sea would avoid saltwater contamination and damage, easing the process of refurbishment and re-use.  Two attempts were made to catch boosters in this manner were made in May and November 2022. The first was initially successful, but the helicopter had to to release the booster second after capture, doing to the hook mechanism failing to fully engage, and the booster plummeted into the sea, its parachute useless.

The November attempt had to be aborted when a telemetry data failure on the booster meant the helicopter could not rendezvous with it and make a capture. However, as the booster was not captured, it was able to make a gently splashdown at sea under its parachute, allowing it to be recovered by a support boat. Examination of the booster on its return to New Zealand revealed it to be in “remarkably good condition”, with most of its components passing their readiness for re-use without the need to be replaced.

As a result, Rocket Lab have decided that further waterproofing the booster for at-sea recoveries and allowing them to be recovered after splashdown would be cheaper than the air recovery, result in a greater level of booster recovery (70% compare to 50% by air), improving overall booster re-use.

Rocket Lab is one of the fastest-growing smallsat launchers in the commercial sector, with the company operating out of Māhia Peninsula, New Zealand and the Mid-Atlantic Regional Spaceport in Virginia, USA. It has been making revenue-earning commercial launches since 2018, and in 2023 is set to double its launch rate to around 16. The company is also developing a medium-lift semi-reusable launch system called Neutron, which is expected to launch up to 8 tonnes if the first stage is recovered, or 15 tonne if used as a fully expendable vehicle. The first launch is expected to come no earlier that 2024, with the rocket capable of eventually being rated for crewed launches.

Transit of Mercury

In February 2020 a United Launch Alliance (ULA) rocket lifted off from Cape Canaveral Space Force Station in Florida, carrying with it the European Space Agency’s Solar Orbiter (SolO) mission, part of a growing flotilla of spacecraft focused on observing the Sun as it goes through the latest in it 11-year cycles of activity.

SolO carries a suite of instruments for studying the Sun, including two imaging systems – the Polarimetric and Helioseismic Imager (PHI) and the Extreme Ultraviolet Imager (EUI). On January 3rd, 2023, both of these instruments witnessed a transit of Mercury across the face of the Sun.

The event was important not just because of the potential for the light of the Sun to reveal hidden secrets of the planet, the solid black circle of the planet presented the perfect opportunity to better observe different layer of the Sun’s atmosphere against the silhouette of the planet. At the same time, it enabled scientists to ensure the imaging systems had been correctly calibrated.

Opportunities to observe Mercury from Earth as it transits the Sun are actually rarer than might actually be appreciated; whilst it sits between Earth and the Sun and orbits the latter every 87.9 terrestrial days, actual transits observable from Earth will only occur 13 times this century, with the last occurring in 2019 and the next in 2032. As such, SolO offered a unique opportunity to capture a new, and much closer / clearer view of one.

SolO achieved its first perihelion pass around the Sun in February 2021 at roughly half the distance Earth is from her parent star. In April 2023, it will make its second close past, just over a quarter of the distance from the Sun to Earth. At the same time, the spacecraft is using the gravity well of Venus to gradually increase its orbital inclination around the Sun, eventually allowing it to start passing over the Sun’s poles from 2025 onwards.