Space Sunday: JWST, Artemis and rockets delivering cargo to Earth

JWST art. Credit stsci.edu

The James Webb Space Telescope (JWST) is due to enter its initial halo orbit around the Earth-Sun L2 position, 1.6 million kilometres beyond Earth’s orbit around the Sun, on Monday, January 24th, 2022.

With the deployment of its major external elements completed, the observatory has been engaged in the first phase of a sensitive operation to correctly align the 18 hexagonal segments of its primary mirror so it perfectly reflects light into the boom-mounted secondary mirror and thence back into the telescope’s interior for delivery to its space science payload.

This first part of what is an extensive operation saw all 18 segments gently eased 12.5 mm away from the mirror’s backing structure, each segment being propelled forward by six tiny motors, referred to actuators. This allowed each mirror segment to be gently moved away from the restraints that held it in place during launch, and provides enough space behind each segment so it can be gently adjusted to align with its companions as the alignment process continues, all of them coming together to form a single, focused parabola.

When it starts, the latter part of the work will involve the actuators moving in the micron and nanometre ranges of movement, and once started, is expected to continue for around 40 days.

However, before that process begins, at 19:00 UTC on Monday, January 24th, JWST will fire its thrusters to ease itself into its initial halo orbit around the Earth-Sun L2 position, marking its arrival in the area of space where it will operate.

Thanks to the sheer accuracy of the Ariane 5 launch vehicle and the “mid-course” correction thruster burns JWST has made en route to this point, it has been calculated the observatory currently has sufficient propellant reserves for at least 10 years of operations. If the insertion burn proves to be as accurate, mitigating any need for it to be further refined, then JWST may have its overall mission length extended a little more.

JWST is due to enter its Earth-Sun L2 Halo orbit on Monday, January 24th, 2022. Credit: NASA

Once safety inserted around the L2 point, the telescope will go through an additional period of cooling adjustment to bring its instruments down to their operational temperatures. This process, which will actually use heaters to ensure heat dissipation is properly controlled, will take a number of weeks to complete, after which the primary mirror alignment process will resume, allowing scientific instrument calibration to commence.

Artemis: No Immediate Second Lunar Landing

After landing astronauts on the Moon in the mid-2020s for the first time in more than a half-century, NASA will wait at least two further years before making a second crewed lunar landing as part of the Artemis program.

Artemis 3 is due to deliver a crew of 2 to the lunar surface in around 2025. However, the next mission slated for Artemis will not follow it to the lunar Surface. Instead, and as indicated at a two-day meeting of the NASA Advisory Council’s Human Exploration and Operations Committee on January 18th/19th, it was indicated that the Artemis 4 mission will target the assembly of the Lunar Gateway.

This is the space station that will be placed in cislunar orbit and used as a transfer station for crews arriving from Earth aboard NASA’s Orion capsule and the Human landing System (HLS) vehicles that will carry them to the surface of the Moon and back. The first elements of the Gateway, the Power and Propulsion Element and Habitation and Logistics Outpost, will be launched together via a SpaceX Falcon Heavy in late 2024. They will then spend a year spiralling around the Moon and settling into their halo orbit.

Artemis 4, which will feature the Block 1B Space Launch System rocket using the powerful Exploration Upper Stage (EUS), intended for heavy cargo launches and deep space missions will carry the International Habitat Module (I-Hab) for the gateway, along with a crewed Orion vehicle that will oversee attaching I-Hab to the Gateway modules already in lunar orbit.

Whilst conceptual in terms of what the Lunar Gateway might eventually become, this image indicates the core NASA NASA elements  – the Power and Propulsion Element and the Habitation and Logistics Output module (which will actually be docked one to the other) to be launched in 2024, and the JAXA / ESA I-Hab module, to be launched in 2025 as part of the Artemis 4 mission. The Orion capsule + service module are also shown. Credit:  NASA

Even with the more powerful EUS replacing the Interim Cryogenic Propulsion Stage that will fly on Artemis 1-3, the Gateway flight of Artemis 4 will be a challenge for the SLS. The Block 1B vehicle will be capable of delivering around 38 tonnes to lunar orbit – and some 27 tonnes of that capability will be taken up by the Orion crew capsule and its service module. That means the European and Japanese space agencies, responsible for providing I-Hab for Artemis, must ensure the module masses no more than 10 tonnes. By comparison, similar modules on the ISS average around 12-12.5 tonnes.

A further reason for focusing Artemis 4 on Lunar Gateway activities is that NASA will not actually have any HLS vehicle(s) at its disposal for lunar landings for a period of time after Artemis 3. In awarding the initial HLS contract to SpaceX to develop a lunar landing variant of its Starship vehicle, NASA did so on the basis of using only a single lunar landing. Once it returns to orbit, the SpaceX HLS will require refuelling in order to make a second trip – and currently, NASA has indicated that it would rather await a “sustainable” HLS system  – to be developed under a new, yet-to-be awarded contract called Lunar Exploration Transportation Services (LETS).

NASA HLS; the current contract with SpaceX is only for a single HLS vehicle (centre). After Artemis 3, the first lunar landing, NASA will be relying on a “sustainable” HLS design – yet to be contracted – which might be Dynetic’s versatile design (l), or the Blue-Origin led design (r), both of which originally competed against SpaceX for the initial HLS contract, or might be provided by another supplier. Credit: Dynetics / SpaceX / Blue Origin

Exactly what is so happen to the SpaceX HLS after Artemis 3 is unclear. That mission will not use the Lunar Gateway, but will see an Orion dock with the SpaceX vehicle in lunar orbit for the 2-person crew transfer. As such, it is entirely possible the SpaceX HLS might simply be “parked” in lunar orbit and left.

However, given any LETS contract has yet to be granted a further crewed landing on the Moon under the Artemis banner is unlikely to occur before late 2027 or (more likely) 2028 / 29.

Continue reading “Space Sunday: JWST, Artemis and rockets delivering cargo to Earth”

Space Sunday: pebbles, ALH84001 and a supernova

Mars 2020 rover Perseverance. Credit: NASA/JPL

NASA’s Mars 2020 rover Perseverance rover is suffering what might considered a case of kidney stones that’s proving hard to clear up.

On December 29th, 2021, the rover drilled into a rock the mission team had dubbed “Issole”, coring the material out using the percussive drill at the end of its 2.1 m robotic arm. The coring went smoothly enough, the sample being cached inside one of the titanium tubes used for obtaining sample that are to be geocached on Mars for future collection by a joint NASA-ESA sample-return mission, however, it was then that a problem occurred.

The rover’s sample-gathering system is actually extremely complex, comprising three separate robotic systems. The first is the robot arm itself, which houses the drill mechanism and bit.

Mars 2020 SHArm robotic arm: hidden underneath the rover, SHArm is responsible for handling sample tubes (highlighted in yellow) before / after they have been used to gather core samples gathered by the rover’s drill. Credit: NASA/JPL

The second is another robot arm called SHArm – the Sample Handling Arm -, tucked into the underside of the rover. Its function is to select unused sample tubes from the storage cache at the back of the rover, and pass them forward so that they can be made available to the robot arm and the drill for sample gathering. This also takes tubes containing samples and delivers them to a number of sub-systems before sealing them and stowing them back into the cache area.

Between these two, and acting as a go-between, is the “bit carousel”. This is a wheel-like robot at the front of the rover. This is a go-between for both the main robot arm and SHArm, allowing empty tubes to be delivered to a position where they can be transferred to the robot arm / drill mechanism, and full tubes to be rotated down to where SHArm can collect them. In all the carousel has capacity for up to 10 full / empty sample tubes as they are moved between the robot arm and SHArm.

The “bit carousel” (highlighted in grey) with the robot arm and the drill head it carries (the large object on the left) transferring a sample core tube (yellow) to one of its transfer recesses. Credit: NASA/JPL

It was when attempting to transfer the tube with the latest sample to the carousel that the problem occurred, prompting the mission team to order Perseverance to return the tube to the drill mechanism and then rotate the robot’s hand to allow the WATSON image to photograph the carousel – revealing small pebbles of rock were caught in the mechanism.

While the carousel is designed to operate with a degree of dirt and debris in its mechanism, the decision was taken to attempt a debris removal operation and essentially “reset” the sample gathering mechanisms. This has also proven to be a complicated operation. Firstly, the carousel had to be carefully images to understand the full extent of the debris distribution. Then the ground beneath the rover needed to be imaged for an initial set of “before” photos.

A WATSON close-up of one of the sample tube recesses in the “bit carousel”, showing some of the pebble-like debris caught in the mechanism. Credit: NASA/JPL

After this, the main robot arm was order to rotate to a position where the current sample tube could be emptied, allowing it to be re-used in a future coring of “Issole”. Then, over the course of the weekend, the entire “bit carousel” was due to be put through two rotation operations designed to help shift some of the debris. Once completed, WATSON will again be used to image the mechanism – and the ground under the rover – to ascertain the status of the debris and what further actions need to be taken to clear the remaining debris.

In all, mission engineers believe it could be the end of the week before the sample system is ready to resume operations, at which point a decision will be taken on whether or not to gather a further sample from “Issole”.

 The Riddle of ALH84001 Finally Resolved?

In 1996 a fragment of a Martian meteorite that was found in the Allan Hills, Antarctica and designated ALH84001 (marking it as the first Martian meteorite found in the area 12 years earlier, in 1984), caused a storm of controversy- which appears to now being laid to rest.

A cartoon by Kevin Kallaugher that appeared in the Baltimore Sun on August 8th, 1996 highlighting the media’s response to the ALH84001 announcement by David McKay and his team

To summarise: when parts of the meteorite were examined by a group of scientists (it is not uncommon for multiple years to pass between meteorites being found , catalogued and stored and actually being examined) announcing they may have found trace evidence of past microscopic life from Mars. Unfortunately, the press responded in a manner typified by a cartoon from the time.

The pronouncement, over-amplified by the press, garnered immediate push-back by others in the scientific community which in turn resulted in the science team – which included David S. McKay, Chief Scientist for astrobiology at the Johnson Space Centre, Texas, during the Apollo programme to double down on their claims they have discovered fossilised Martian bacteria.

Since then, the debate concerning how the objects –  chain structures nanometres in length resembling living organisms – and whether or not they might be organic in origin has raged back and forth – although it did diminish somewhat following McKay passing away in 2013. Not another team of scientists believe they have definitive proof that whilst the structures were organic in nature, they are not signs of life having once been active on Mars.

Instead, the new study – the result of an extensive study of ALH84001 samples and all that has been learned about it in the intervening 25 years – points to the organic structures being the result of abiotic organic chemistry – that is, they formed as a result of chemical reactions between water and rock that did not involve any genuine organic processes.

The chemical interactions likely took place around 4 billion years ago – at a time when Mars was believed to be much warmer and wetter than it is now, and a time when life might have originated on the planet. However, in the case of ALH84001, the team carrying out this study found that the organic compounds in the meteorite are closely associated with serpentine-like minerals. Serpentine is a dark green mineral, sometimes mottled or spotted like a snake’s skin, that is associated with once-wet environments.

On Earth, this kind of association between organics and serpentine is often associated with water percolating / circulating through magnesium-rich volcanic rocks change their mineral nature, producing hydrogen. If the water is slightly acidic and contains dissolved carbon dioxide, it can additionally result in carbonate minerals also being deposited…When taken together, these two processes – referred to as serpentinization in the case of the first and carbonation in the second – can result in deposits that appear to be of an entirely organic origination.

An electron microscopy image showing chain structures resembling living organisms fossilised in meteorite fragment ALH84001. Credit: NASA

Given the rocks in which ALH84001 were formed 4 billion years ago and were exposed to a long period of repeated water interaction, and the similarity they share with similar abiotic mineral deposits found on Earth, the team believes they are more than likely of a similar, non-organic origin.

However, the study doesn’t discount the potential for life to ever have arisen on Mars – it may actually strengthen it. This is because while these abiotic processes are not the result of organic processes, they do leave deposits of chemicals and minerals that can go on to help kick-start microbial life. What’s more, the sheer age of the ALH84001 marks it as the first Martian rock fragment that is old enough to provide evidence that abiotic processes were at work at a time when Mars was warm and wet – and when other processes may have been at work that might have utilised the deposited compounds to get basic life started. And if the rocks in which ALH84001 formed – there may be other similar ancient deposits on the planet that microbial life may have been leveraged.

Astronomers Witness a Star’s Death and a Supernova’s Birth in Real-Time

For the first time, a team of astronomers have imaged in real-time as a red super giant star reached the end of its life, watching as it convulsed in its death throes before finally exploding as a supernova.

The star was about 10 times more massive than the Sun and lay within the NGC 5731 galaxy about 120 million light-years away – meaning what astronomers saw actually occurred 120 million years ago.

In the summer of 2020, astronomers using the Pan-STARRS observatory on Haleakala, Maui noticed the progenitor tar suddenly go through a dramatic rise in luminosity. This warned them something massive was about to happen, focusing attention at Pan-STARRS on the star, and also brought in the W. M. Keck Observatory on Mauna kea, Hawaii Island in to observe the star as it collapsed over 130 days, before it gave a bright flash prior to its final exceptionally violent detonation into supernova SN 2020tlf..

The data from the observations is relatively boring – the star was far, far, far too far away to be actually images by either observatory, so it amounts to lines and dots on a chart. However, it has allows the event to be computer modelled. More particularly, the event has given astronomers first-hand insight into a supernova event involving a red super giant, and raised some puzzling questions.

For a red super giant to go supernova is not uncommon. Normally, however, there is a period of shrinkage and material ejection, referred to as circumstellar material (CSM) prior to core collapse. But that process generally takes place on a much longer timescales than the 130 days experienced by SN 2020tlf, suggesting something unusual or unexpected was taking place within the star.

In addition, the mysterious bright flash prior to the final detonation was unexpected and – thus far – unexplained, although it is thought it be somehow related to the ejected CSM – although astronomers are currently at a loss to explain what this might be. The flash appears to also be liked to a mammoth ejection of gas from the star, another aspect that doesn’t fit with established understanding of red super giant supernovae.

All of this adds up to the end of the star and the birth of SN 2020tlf being far more violent that has been the accepted case for red super giants. The question now is: was this event out of the ordinary for such stars, or does it reflect a more expected behaviour for them. However, given the sudden rise in luminosity witnessed ahead of the event, astronomers involved in projects such as the Young Supernova Experiment now have a clue to what to look for when seeking future potential red super giant supernovae.

Space Sunday: JWST and more 2022 highlights

JWST art. Credit stsci.edu

The James Webb Space Telescope (JWST) has completed deploying all of its major components whilst en route to its operational orbital position at the Earth-Sun Lagrange L2 position.

At the time of my last update, NASA was expected to start work on tensioning-out the layers of the observatory’s layered sunshield. However, this was delayed in preference of working on JWST’s power subsystem. The decision came as a result of telemetry showing the observatory’s solar arrays were not producing their anticipated output due to them operating at their factory defaults. After re-balancing them, engineers took the opportunity to gather a baseline of power requirements for future reference, and to ensure the motors that are key to the sunshield tensioning process were at their optimal temperatures prior to starting the tensioning operation.

The work on the power subsystem meant that tensioning operations did not start until January 3rd. This comprised each of the hair-thin layers of the sunshield being gently tensioned out and separated from the other layers to allow it to function most efficiently in absorbing / reflecting heat and sunlight. By the end of the 3rd, three of the five layers had been correctly tensioned, putting the operation well ahead of schedule, allowing the operation to be completed with the tensioning of the last two layers on Tuesday, January 4th.

This left the way clear for the deployment of the observatory’s secondary mirror system. Commencing on January 5th,  this involved unfolding a series of booms called the Secondary Mirror Support Structure (SMSS) to extend the secondary mirror assembly out in front of the primary mirror, allowing it to gather and focus the light from the primary back through an aperture at the centre of the primary, where a third mirror reflects it down into the observatory’s interior and to its instruments.

JWST secondary mirror deployment. Credit: NASA

On January 6th JWST deployed the radiator systems that serve to remove excess heat from the observatory. Stowed flat against the rear of the main mirror assembly, the radiator panels were successfully extended out and away from the body of the observatory, freeing the mechanisms required to unfold the two “wings” of the primary mirror.

At 6.5 metres in diameter, and comprising 18 hexagonal gold-covered segments JWST’s primary mirror is too big to fit in the payload fairings of any operational launch vehicle, thus the use of the two “wings” to the port and starboard sides of the mirror.

Work started on unfolding these on January 7th, commencing with the port wing. The operation commenced at 14:30 GMT, the wing unfolding in five minutes  – although latching it into place took a further two hours. A similar operation was then initiated on January 8th to deploy the mirror’s starboard wing, with telemetry received at 18:17 GMT to confirm it had locked into place in its deployed configuration.

Unfolding one of JWST’s primary mirror segments. Credit: NASA

The successful unfolding and latching of the primary mirror segments marked the end of the deployment phase of the mission, allowing the JWST mission and engineering teams to move onto the commissioning phase of the mission.

In all, this will take some five months to complete; the first part of which involves correctly align the 18 individual mirrors that make up the observatory’s primary mirror so that they all work in concert to gather and reflect light into the secondary mirror. This is a multi-step process, in which each of the 18 segments is gently adjusted by means of 6 actuators located behind it to ensure proper alignment – with the secondary mirror also having actuators that allow minute adjustments to be made to it, assisting the alignment process whilst ensuring the gathered light remains correctly focused on the non-moveable third mirror. It is not an easy process, the work is expected to run the full 120 days of the commissioning period.

2022 Space Highlights II

In the last instalment of Space Sunday, I mentioned some of the forthcoming missions planned for 2022. In addition to those I mentioned then (limited by space), here are some more – all of which I hope to cover in more detail as the year progresses.

  • Axiom missions to ISS: Axiom Space plan to launch two “all private” missions to the International Space Station (ISS) utilising SpaceX Falcon 9 and Crew Dragon. Each mission will last around 8 days and focus on science and educational outreach. The first mission will launch at the end of February 2022, and the second in the autumn.
  • Jupiter Icy moons Explorer (JUICE) mission: ESA’s mission to Jupiter, to primarily study three of its moons – Ganymede, Europa and Callisto – should launch in May 2022. Arriving in Jovian orbit in 2029, it will then create a 3-year study mission.
  • Psyche asteroid mission: set for July 2002 and launched via a Falcon Heavy booster, NASA’s Psyche mission will study a metallic asteroid of the same name that orbits the Sun between Mars and Jupiter. It is believed the asteroid is the exposed nickel-iron core of an early planet. Thus, studies of it may offer new clues about how terrestrial planets like Earth form.
  • India’s Gaganyaan space missions: India plans to complete an uncrewed launch of its new Gaganyaan crew vehicle in summer 2022, with a second test flight before the end of the year.
An artist’s impression of India’s Gaganyaan crew capsule and is service module. Credit: ISRO
  • ExoMars Rover launch: the long-awaited European Mars rover mission will launch between August and October, carrying the Rosalind Franklin rover to Mars. Once there it will join the ExoMars Trace Gas Orbiter (TGO), which arrived at Mars in 2016, to study the red planet.
  • Dream Chaser ISS operations commence: Sierra Nevada Corporation’s Dream Chaser Cargo space plane will commence resupply flights to the ISS, carrying up to 5 tonnes of supplies and equipment to the station and returning around a tonne to Earth. The maiden Dream Chaser launch will mark the second flight of ULA’s new Vulcan rocket.
  • Lunar missions:
    • US Nova-C lunar lander: the Intuitive Machines Nova-C land will launch atop a SpaceX Falcon 9 vehicle early in 2022, carrying five NASA Commercial Lunar Payload Services (CLPS) payloads to the Mare Serenitatis, including a UK-built lunar rover.
    • Russia: the Luna 25 robot mission to the Moon’s South Pole will launch in July, marking the first Russian mission to the Moon in 45 years, and the first to land in the lunar Polar Regions. It will carry nine instruments to research the lunar regolith and exosphere (atmosphere).
Russia’s Luna 25 under construction. Credit: Roscosmos
    • NASA lunar drilling mission: scheduled for launch in December 2022, the Polar Resources Ice Mining Experiment-1 (PRIME-1) is the first-ever mission designed to harvest water ice from inside the moon — a resource NASA hopes to utilize for its Artemis program.

In Brief

Biden White House Commits to ISS Extension

The Biden administration  has formally supported extending operations of the International Space Station through the end of the decade, an announcement that is neither surprising nor addresses how to get all of the station’s partners, notably Russia, to agree on the station’s future.

NASA has wanted to continue operating the ISS through until 2030 for several years, but has lacked outright political support to do so. In 2018, the US Senate agreed to extend US ISS operations through until 2028 or 2030, but the move failed to gain the required two-third House majority in order to pass. Support from the White House may help the agency gain full US support for the mission, and as a result of it, the European Space Agency has further indicated it would seek a resolution among members to continue to fund their side of station activities.

However, the major sticking point for operations lies with Russia. Most of the Russian modules on the station are growing increasingly old and subject to failure, and as such, Roscosmos is reluctant to continue supporting operations beyond 2024. In addition, geopolitics may impact the future of the ISS: Russia has already announced plans to operate its own space station at the expense of continued international cooperation with the ISS.

China Complete Key Station Robot Arm Test

On Thursday, January 6th, a large robotic arm on China’s space station successfully grasped and manoeuvred a cargo spacecraft in a crucial test ahead of upcoming module launches.

An artist’s impression of the robot arm test on the Chinese space station. Credit CMSAThe 10 metre long robotic arm on the Tianhe-1 module of China’s new Tiangong space station was used to grasp Tianzhou-2 supply vehicle that has been docked with the module since the end of May 2021, and move out away from the station, angling it through 20 degrees before returning it to the Tianhe-1’s forward docking port, where it reattached itself.

The 47-minute operation began at 22:12 UTC, as was designed to test the robot arm’s ability to manipulate and move large modules that will form a part of the station as it progresses. In particular, the test is vital to China’s plans to launch two science modules – called Wentian and Mengtian – to dock with Tianhe-1 in May / June and August / September 2022 respectively, thus completing the Tiangong space station.

Hubble Space Telescope’s One  Billion Seconds

One January 1st, 2022, the Hubble Space Telescope (HST) achieved another milestone in its distinguished career – notching up 1 billion seconds in orbit since its launch on April 24th, 1990. That’s 31.7 years of near-continuous operations in Earth’s orbit.

A joint NASA / ESA project, HST has contributed massively to our understanding of the solar system, our galaxy and the universe as a whole. Despite recent issues with the observatory, it is hoped that HST will continue to operate through the 2020s and well into the 2030s.

Space Sunday: JWST and 2022 highlights

An artist’s impression of the James Webb Space Telescope (JWST) with Earth and the Sun beyond. Credit: ESA/ATG medialab
Following its launch on December 25th, the James Webb Space Telescope (JWST) has completed several major steps in the deploying its critical hardware as it continues its month-long voyage towards its operational orbit at the Earth-Sun L2 Lagrange point.
Here’s a brief summary of what has happened thus far with deployments.

In the early houses of Wednesday, December 29th (UTC), Earth, JWST unfolded the forward sunshield pallet, lowering it away from its stowed position in front of the central deployable tower supporting the (still folded) primary and secondary mirror assemblies and the telescope’s massive radiator, and containing JWST’s vital electronics and science instruments.

Unfolding the after sunshield pallet. Credit: NASA

The lowering process took 20 minutes to complete, and was followed by the aft sunshield pallet being unfolded from behind the mirror tower in an 18-minute operation. After this, JWST went through several hours of additional operations, including ensuring the pallets were correctly in place and their sub-systems operational, and orienting the observatory with respect to the Sun to provide optimal shielding when the sunshield is deployed and tensioned. Once all this was completed, the command was given for the pallets to lock themselves in their deployed condition.

Later on the 29th, the deployable tower was raised some 1.2 metres from its “stowed” state over a 6-hour period. This moved it away from JWST’s thrusters and provided the room needed for the sunshields to be deployed and tensioned.

A computer generated simulation of one of JWST’s boom being extended, drawing out the sunshield membranes. Credit: NASA

Thursday, December 30th saw the deployment of the sunshield commence. A three-part process, and one vital to the observatory’s operations, this started with the drawing back of the membranes that have protected the delicate sunshield.

On December 31st, the booms that extend the five layers of the sunshield were extended. Operations began at 18:30 UTC, with the five segments of the portside boom extending outwards from the mid-point between the two sunshield pallets. The procedure took just over three hours to complete, and was followed by the extension of the starboard boom, which took a similar amount of time, also drawing out the membranes of the sunshield on that side of the telescope.

A computer generated simulation of one of JWST’s boom being extended, drawing out the sunshield membranes. Credit: NASA

Overall, the deployment of both booms took longer than anticipated, but was successfully completed, with operations then being halted for New Years Day. On January 2nd, operations resumed on the tensioning of the membranes. A 2-day operation, this involves separating each of the 5 membranes from the others and then tensioning it using the side booms and four fore-and-aft boom mechanisms. Once this has been completed, the focus will switch to deploying the telescope’s “eyes” – its secondary and primary mirrors.

The other news on the programme is that such was the accuracy with which the Ariane 5 placed JWST onto its transfer orbit, coupled with the smoothness of the first “mid-course” thruster burns, far less propellants that had been estimated. This now means that the observatory has sufficient reserves to complete at least a 10-year mission (although NASA remains focused on the 5-year primary mission).

Space Highlights for 2022

I generally try to look ahead to key space events at the start of the year, and while this may not be as comprehensive as previous years, but the following is offered as a broad summary of high points.

Launches

Several new launch vehicles will undergo initial launch tests / flight in 2022, including:

  • Block 1 NASA Space Launch System (USA): maiden flight, February 2022 carrying the Artemis 1 mission hardware and cubesats for ten missions in the CubeSat Launch Initiative (CSLI), and three missions in the Cube Quest Challenge. The payloads will be sent on a trans-lunar injection trajectory.
Artemis 1 mission – click for full size. Credit: NASA

Continue reading “Space Sunday: JWST and 2022 highlights”

Space Sunday: JWST and a touch of SpaceX

The James Webb Space Telescope. Credit: NASA

The world’s largest and most powerful space telescope yet built – the James Webb Space Telescope (JWST) – finally made its way into space on Christmas Day, December 25th, 2021, marking the start of a mission almost 30 years in the making.

That mission is multi-part in its scope, encompassing as it does looking back to the origins of the universe and the galaxies around us, together with gaining a greater understanding of the nature and formation of galaxies, stars and planetary systems, and learning more about the nature of worlds beyond our own solar system, as well as seeking signs of the potential origins of life. It is a mission that has been plagued by technical and other issues that have repeatedly delayed its launch – and high winds along its path of ascent to orbit caused one final delay, pushing the launch back from Christmas Eve to Christmas day.

Final countdown commenced several hours ahead of lift-off, with the Ariane 5 launch vehicle igniting its engines as scheduled at 12:20 UTC, rising into the sky over the European Spaceport near Kourou, French Guiana, carrying the US $10 billion telescope on the first leg of a journey to its operational destination that will take it almost a month to complete. Along the way it will go through a series of complex activities along the way, each one vital to its operational success.

The European Ariane 5 launch vehicle carrying JWST (designated flight VA256) lifts-off from the European spaceport, French Guiana, December 25th, 2021. Credit: ArianeSpace / ESA / NASA

The first three of these activities came just half-an-hour after lift-off, with the separation of the telescope from its Ariane upper stage after the latter had boosted it onto the start of its 1.6 million kilometre journey away from Earth. Almost at the same time, JWST deployed the solar array vital for supplying it with electrical power. This was followed two hours later by the deployment of the high gain communications antenna and, 12 hours after launch, JWST completed the first “mid-course” correction to its trajectory, steering itself more closely towards its final destination.

This destination lies close to the Earth- Sun L2 Lagrange point, 1.6 million km further out from the Sun than Earth’s orbit, but which orbits the Sun in the same period of time as Earth. It’s a location selected for JWST’s operations for a number of reasons, including:

  • It effectively puts the Earth, Moon and Sun “behind” the telescope, affording it uninterrupted views of the solar system and all that lies beyond it.
  • It is a semi-stable position in space that orbits the Sun at the same time as Earth. This both allows for continuous direct-line communications, and reduces the amount of propellants JWST would otherwise require for basic operations such as station-keeping and orbital corrections.

Even so, operations at the position will not be straightforward. As the L2 position is a point of gravitational equilibrium, JWST will operate in an orbit 800,000 km wide around it. Whilst relatively stable, this orbit will require JWST to make small periodic adjustments every 23 or so days. Given it can only carry a finite amount of propellants (168 kg) for these adjustments, the telescope effectively has an operational “shelf life”: it’s primary mission is set at just 5 years – although it is hoped it has sufficient propellants for at least 10 years worth of controlled observations.

Having been launched in a “packed” form that allowed it to fit inside the payload fairing of its launch vehicle, JWST will spend the next two weeks gradually “unfolding” itself, as per the video below, with a number of firings of its thrusters to fine-tune its flight to its intended orbit.

All of these activities are vital to JWST being able to perform its desired mission, but perhaps the two most important are the deployment of the telescope’s secondary and primary mirrors, and that of its incredible and delicate heat shield.

The optics deployment will see the booms supporting the secondary mirror that reflects light gathered from the primary back to where it can be delivered by a third mirror to the instruments deep inside JWST. The second part comes with the unfolding of the “table flap” elements of the primary mirror, allowing it to reach its full 6.5 metre diameter, almost 2.5 times the diameter of the primary mirror on the Hubble Space Telescope. (HST), and with potentially 100 times its power.

JWST is primarily intended to operate in the infrared, but in order to do so, its instruments and science systems must be kept very cold. If any of them exceed 50ºK (-223.2ºC), the heat they generate will be registered in the infrared; potentially overwhelming the telescope’s ability to capture the infrared light of stellar objects. Given that JWST will be in permanent sunlight, maintaining such an incredibly low temperature this is a considerable challenge – hence the vital role of JWST’s remarkable heat shield.

How the heat shield will keep the operational surfaces of JWST super-cold. Credit: NASA

This comprises 5 layers of Kapton E polymide formed into sheets as thin as a human hair and then covered on both sides with a thin membrane of aluminium, this shield is carried folded within two “pallets” that also need to be unfolded to form the “base” of the telescope.

Once these pallets have unfolded, booms can be extended on either side of JWST, allowing the 5 layers of the heat shield to be unfurled like the sails of a ship, and then tensioned off. This will provide an area of shadow the size of a tennis court within which the instruments and optics of the telescope will sit, while radiators behind the main mirror will circulate the heat absorbed by the shield and radiate it back into the cold shadow without impacting telescope operations.

Continue reading “Space Sunday: JWST and a touch of SpaceX”

Space Sunday: touching the Sun and Martian organics

Parker Solar Probe. Credit NASA

The Parker Solar Probe has finally reached the atmosphere of the Sun.

The NASA spacecraft has spent more than three years winding its way by planets and creeping gradually closer to our star to learn more about the origin of the solar wind, which pushes charged particles across the solar system.

Since solar activity has a large effect on living on Earth, from generating auroras to threatening infrastructure like satellites, scientists want to know more about how the Sun operates to better make predictions about space weather, and gain a better understanding of the mechanisms at work in and around our star. Over the years, we’ve done this with a number of missions – but the most fascinating of all to date is the Parker Solar Probe, a NASA mission that has literally touched the face of the Sun.

The spacecraft – launched in 2018 – is in a complex dance around the Sun that involves skimming closer and closer to our life-giving star, and they sweeping away again, far enough to cross back over the orbit of Venus – indeed, to use Venus as a means to keep itself looping around the Sun in orbits that allow it to gradually get closer and closer, with the aim of actually diving into and out of the Sun’s corona, what we might regard as the Sun’s seething, broiling atmosphere.

In fact, the probe actually first flew through the corona in April 2021; however, it was a few months before the data to confirm this could be returned to Earth, and a few more months to verify it; hence why the news has only just broken about the probe’s success. One of the aims of pushing the probe into the Sun’s corona was to try to locate the a boundary called the Alfvén critical surface. This is the boundary where the solar atmosphere  – held in check by the Sun’s gravity – end, and the solar wind – energetic particles streaming outwards from the Sun with sufficient velocity to break free of that gravity – begins, creating the outwards flow of radiation from our star.

Up until Parker’s April 2021 passage into the corona, scientists has only been able to estimate where Alfvén critical surface lay, putting it at somewhere between 6.9 million and 13.8 million km from the gaseous surface of the Sun. As it passed through the corona, Parker found these estimates to be fairly accurate: the data it returned to Earth put the outer “peaks” of the boundary at 13 million km above the Sun’s surface – or photosphere; the data also revealed the boundary is not uniform; there are “spikes and valleys” (as NASA termed them) where the boundary stretches away from the photosphere at some points, and collapses down much close to it in others. While it has yet to be confirmed, it is theorised this unevenness is the result of the Sun’s 11-year active cycle and various interactions of the atmosphere and solar wind.

The Parker Solae Probe. Credit: NASA / I. Pey

The April “dip” into the corona lasted for five hours – as the mission goes on, future “dips” will be for longer periods). But give the spacecraft is travelling at 100 kilometres per second, it was able to gather a lot of data as it zipped around the Sun – and even sample the particles within the corona. The probe’s passage revealed that the corona is dustier than expected, the cause of which has yet to be properly determined, as well as revealing more about the magnetic fields within the corona and how they drive the Sun’s “weather”, generating outbursts like solar flares and coronal mass ejections (CREs), both of which can have considerable impact on life here on Earth.

To survive the ordeal of passing through the corona, where temperatures soar to millions of degrees centigrade, far hotter than those found at the Sun’s photosphere.  – Parker relied on its solar shadow-shield: a hexagonal unit 2.3 m across made of reinforced carbon–carbon composite 11.4 cm thick with an outer face is covered in a white reflective alumina surface layer. This shield is so efficient in absorbing / reflecting heat, whilst passing through the corona the sunward face is heated to around 1,370ºC, but the vehicle, sitting inside the shadow cast by the shield never experiences temperatures higher than 30ºC.

In addition to mapping the Alfvén critical surface, Parker’s April 2021 trip into the Sun’s corona, the probe also passed through a “pseudostreamer,” one of the huge, bright structures that rise above the Sun’s surface and are visible from Earth during solar eclipses. This was compared to flying into the eye of a storm the probe recorder calmer, quieter conditions within the streamer, with few energetic particles within it. Exactly what this means is again unclear at this time, but it does point to further incredibly complex actions and interactions occurring with the Sun.

Since April, Parker has dipped back into the corona twice more, with the November 2021 passage bringing it to around 9.5 million km of the Sun’s photosphere – although again, the data from that pass has yet to be received and analysed. The next passage in February 2022 will again be at roughly the same distance from the photosphere, with a further five passes to follow at the same distance in 2022/23, before a flyby of Venus allows Parker to fly even deeper in to corona. By December 2025, and the mission’s final orbits, it will be descending through the corona to just 6.9 million km from the photosphere.

An artist’s depiction of magnetic switchbacks in the solar wind. Credit: NASA Goddard/CIL/Adriana Manrique Gutierrez

But that’s not all. Because Parker is in an elliptical around the Sun, it spends a part of its time much further away. This both allows the craft to dissipate absorbed heat from its shield, and for it to observe the Sun from a distance, giving scientists much broader opportunities to study the Sun, such as allowing them to study the physics of “switchbacks”. These are zig-zag-shaped structures in the solar wind, first witness by the joint ESA-NASA Ulysses mission that occupied a polar orbit around the Sun in the 1990s.

In particular, Parker’s observations suggest that rather then being discrete events, switchbacks occur in patches, and that these “patches” of switchbacks are aligned with magnetic funnels coming from the photosphere called called supergranules. These tunnels are thought to be where fast particles of the solar wind originate; so switchbacks may have something of a role to play in the generation of the solar wind or they may be a by-product of its generation or, given they seem to have a higher percentage of helium than other aspects of the solar wind, may serve a highly specialised role as a part of the solar wind.

Right now, scientists are unclear on what might be the case, or what actually generates switchbacks; but gaining clearer insight into their creation, composition and interaction with other particles in the solar wind, and with the Sun’s magnetic field might provide explanations for a number of solar mechanisms, including just why the corona is so much hotter than the photosphere.

Mars 2020 Mission Update

Scientists with NASA’s Mars 2020 Perseverance rover mission have discovered that the bedrock their six-wheeled explorer has been driving on since landing in February likely formed from red-hot magma. It’s a discovery with implications for our understanding and accurately dating critical events in the history of Jezero Crater – as well as the rest of the planet.

Even before the Mars 2020 mission arrived on Mars, there have been much debate about the formation of the rocks in the crater: whether they might be sedimentary in origin, the result compressed accumulation of mineral particles possibly carried to the location by an ancient river system, or whether they might be they igneous, possibly born in lava flows rising to the surface from a now long-extinct Martian volcano. However, whilst studying exposed bedrock at location dubbed “South Séítah” within Jezero, the science team noted a peculiar rock they dubbed “Brac”, selecting it as a location from which to collect further samples of Martian bedrock using the rover’s drill.

When taking samples of this kind, booth Perseverance and her elder sister, Curiosity, operating in Gale Crater half a world away, are both instructed to scour target rocks clean of surface dust and dirt that otherwise might contaminate samples. This is done by using an abrasion tool (think wire brush) mounted alongside the drilling mechanism. However, in checking the work on “Brac”, the mission team realised the abrasion process had revealed the rock was rich in crystalline formations.

Rather than going ahead and drilling the rock for a sample, scientists ordered the rover to study the formations using the Planetary Instrument for X-Ray Lithochemistry (PIXL) instrument  – which is designed to map the elemental composition of rocks. PIXL revealed the formations to be composed of an unusual abundance of large olivine crystals engulfed in pyroxene crystal, indicating the formations grew in slowly cooling magma, offering some confirmation that volcanism has at least be partially involved in Jezero Crater’s history. However, PIXL’s data also suggested the rock, once hardened, has subsequently altered as a result of water action – confirming free-flowing water also had a role to play in the crater’s past..

The crystals within the rock provided the smoking gun … a treasure trove that will allow future scientists to date events in Jezero, better understand the period in which water was more common on its surface, and reveal the early history of the planet. Mars Sample Return is going to have great stuff to choose from.

– Ken Farley, Perseverance Project Scientist

The Sample Return mission has yet to be fully defined, let alone funded, but is being looked at as a mission for the early 2030s, quite possibly with European Space Agency involvement. In the meantime, a question Farley and his colleagues would love to answer is whether the olivine-rich rock formed in a thick lava lake cooling on the surface of Mars, or originated in a subterranean chamber that was later exposed by erosion; knowing the answer to this could determine the early history of Jezero Crater and its surroundings.

This 60-second video pans across an enhanced-color composite image, or mosaic, of the delta at Jezero Crater on Mars. The delta formed billions of years ago from sediment that an ancient river carried to the mouth of the lake that once existed in the crater. Taken by the Mastcam-Z instrument aboard NASA’s Perseverance rover, the video begins looking almost due west of the rover, and sweeps to the right until it faces almost due north.

Also within the latest updates from the Mars 2020 team is the news that Perseverance has found organic compounds within the rocks of Jezero Crater and in the dust that covers them. This discovery was made as a result of a review of findings from the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument.

This does not mean that the rover has discovered evidence of past microbial life on Mars; these carbon compounds can be created by both organic and inorganic processes. However, the fact that they have been found at a number of locations explored by the rover means that the science team can map their spatial distribution, relate them to minerals found in their locations, and thus both further determine their organic / inorganic origins and trace the distribution of minerals, etc., within the crater.

Further, the fact that compounds like these have been identified by both the Curiosity and Perseverance rovers means that potential biosignatures (signs of life, whether past or present) could be preserved, too. IF so, then assuming they exist, there may come a time when one our other rover might happen upon them.

Continue reading “Space Sunday: touching the Sun and Martian organics”