Space Sunday: black holes, UK launches & a Chinese sentinel

An image of the super-massive black hole (SMBH) at the centre of our galaxy, as released by the Event Horizon Telescope (EHT) team, May 12th, 2022. Credit: European Southern Observatory (ESO) / EHT

On Thursday May 12th, 2022, the consortium of global observatories that calls itself the Event Horizon Telescope (EHT) announced it had successfully imaged the super massive black hole (SMBH) residing at the centre of our galaxy. It’s not the first time such a SMBH has been imaged – EHT captured the first direct look at one back in 2019, when it observed the black hole at the centre of the supergiant elliptical galaxy Messier 87 (M87*, pronounced “M87-Star”) 55 million light years away, but is still a remarkable feat.

Sitting at the centre of our galaxy and a “mere” 27,000 light years from Earth, Sagittarius A* (pronounced “Sagittarius A Star” or Sgr A*, and so-called because it lies within the constellation of Sagittarius close to the boundary with neighbouring of Scorpius when viewed from Earth) is some 51.8 million km in diameter and has an estimated mass equivalent to 4.154 million Suns.

A composite image showing three of the radio telescopes in the European Southern Observatory’s Atacama Large Millimeter/submillimeter Array (ALMA), Chile, aimed towards the heart of our galaxy and the location of Sgr A*  (image inset). Note the fourth telescope in the background of the image is not aimed at the same point. Credit: ESO/José Francisco Salgado (josefrancisco.org) / EHT

Because of its distance and size (in terms of SMBHs, it is actually fairly middling (M87*, by comparison has a mass somewhere between 3.5 and 6.6 billion Suns) and factors such as the volume of natural light and interstellar dust between Earth and Sqr A*, we cannot see it in the visible light spectrum.

However, we can detect the infra-red radiation from the space around it. This is important because black holes are surrounded by an accretion disk – material attracted by the gravity well of the black hole and which fall into an orbit around it just beyond the event horizon. This material is travelling as such massive speed, it creates high-energy radiation that can be detected.

Even so, gathering the necessary data to image an SMBH, even one as relatively close to Earth as Sgr A* or as incredibly huge as M87* (which is thousands of times bigger than Sgr A*) requires an extraordinary observation system. Enter the Event Horizon Telescope (EHT).

This is actually a network of (currently) eleven independent radio telescopes around the world. It extends from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, and the Very Long Baseline Array (VLBA) in New Mexico, USA, down to the South Pole Telescope (SPT) located at the Amundsen–Scott South Pole Station, Antarctica; and from the James Clerk Maxwell Telescope and the Submillimeter Array, Hawaii to the Northern Extended Millimeter Array on the Plateau de Bure in the French Alps.

The EHT network of observatories. Credit: ESO / EHT via Wikipedia

Together, the telescopes work like this: as the Earth spins, the target object rises over the horizon for some of the telescopes, they all lock onto it with millimetre precision, and track it across the sky. As more telescopes in the network are able to join in, they do, while those passing beyond the point where they can see the target cease observations until the Earth’s rotation brings the object back into view.

This effectively turns Earth itself into a massive radio telescope using Very Long Baseline Interferometry (VLBI), with all of the telescopes gathering an immense amount of data at resolutions far in excess of anything the individual telescopes could achieve. So much data, in fact, that the images of Sgr A* released by the EHT actually don’t do genuine justice.

This is because the total amount of image data gathered by EHT amounts to 3.5 petabytes (that’s equivalent to 100 million Tik Tok videos for the young ‘uns out there!). In order to produce images that could be easily transmitted over the Internet, this data had to be compressed and altered. In fact, the data volume was so huge, it was easier to remove the hard drives containing it and shipping them to the various centres around the world wanting to analyse the data, rather than trying to transmit the data between different locations!

The data were gathered over the course of multiple nights of observations performed by the telescopes in the network in 2017, and it has taken 5 years of analysis using a batch of super computers for the researchers to reach a consensus. This was in part due to the nature of Sgr A* itself. The EHT team had cut their teeth observing M87*, but in terms of imaging, Sqr A* is completely different, as EHT team member Chi-kwan Chan explains:

The gas in the vicinity of the black holes moves at the same speed – nearly as fast as light – around both Sgr A* and M87*. But where gas takes days to weeks to orbit the larger M87*, allowing us to gather consistent images over days. The material around the much smaller Sgr A* it completes an orbit in mere minutes. This means the brightness and pattern of the gas around Sgr A* were changing rapidly as we were trying to image it, so it was a bit like trying to take a clear picture of a puppy quickly chasing its tail.

– Chi-kwan Chan, Steward Observatory, University of Arizona

However, one thing did emerge as processing continued: despite being very different in almost every respect, both M87* and Sgr A* have produced images that are remarkably similar. That they do is seen as a further proof of Einstein’s theory of general relatively, with both accretion disks conforming to his predictions of what should be seen, despite the – no pun intended – massive differences in their nature.

And that’s the key factor in studies like this: they do much to help increase / confirm our understandings of the cosmos around us (or at least, reveal what we theorise to be the case is actually the case). With M87* and Sgr A*, the data gathered are allowing scientists to formulate and model a “library” of different simulated black holes. This library in turn enables researchers test the laws of physics under different domains and offer opportunities to better understand the formation, life and death of galaxies and the very nature of SMBHs themselves, which are believed to be the “powerhouses” of massive galaxies.

Despite being – quite literally – massively different and exhibiting very different natures, when imaged in the infra-red, M87* (55 million light years away at the heart of the M87 galaxy) and Sgr A* (27,000 light years away at the heart of our galaxy) produce remarkably similar images, both of which conform to Einstein’s theory of general relativity. Credit: ESO / EHT

One of the things the EHT observations of Sgr A* have confirmed is that it is actually quite “tame”. In contrast to the idea of the black hole “sucking in” any and all material straying too close to it, it does nothing of the sort – and this appears to be typical for black holes of all sizes.

If Sagittarius A* were a person, it would consume a single grain of rice every million years. Only a trickle of material is actually making it all the way to the black hole. Sagittarius A* is giving us a view into the much more standard state of black holes: quiet and quiescent. M87 was exciting because it was extraordinary in size and power. Sagittarius A* is exciting because it’s common.

– Michael Johnson, Harvard/Smithsonian Centre for Astrophysics

Continue reading “Space Sunday: black holes, UK launches & a Chinese sentinel”

Space Sunday: aerial views, infra-red images & a few notes

Debris Field From the Mars 2020 mission entry, descent and landing (EDL) systems as seen by the Ingenuity helicopter drone during its 26th flight on April 19th, 2022: to the left, the shattered backshell that helped protect rover and helicopter during entry in the Martian atmosphere. and to the right, the collapsed supersonic parachute that slowed the descent to subsonic speeds. Credit: NASA/JPL

Ingenuity, the Mars 2020 mission’s helicopter drone completed its 26th flight on April 19th, and it was something very special, as NASA revealed in a mission update published on April 27th.

As I reported in a recent Space Sunday article, the Mars 2020 rover Perseverance passed close to where its aeroshell – called the backshell – and the parachute used during the descent through the Martian atmosphere had landed after the rover and its rocket-powered skycrane had departed, and was able to image both from a distance at ground level. For its 26th flight, Ingenuity was tasked with flying over and around both backshell and parachute and taking a series of images.

Graphic showing the Mars 2000 EDL – entry decent and landing – and the use of the backshell and parachute. Credit: NASA/JPL

During the mission’s arrival on Mars in February 2021, both the aeroshell and the parachute performed vital roles. The former protected the rover and skycrane from the heat generated through the entry into Mars’ atmosphere and its supersonic descent, whilst the latter slowed that supersonic descent to subsonic speeds, allowing the rover and its rocket-propelled skycrane to drop free and fly clear.

Once separated, the backshell and parachute continued their descent and, in a very practical demonstration on why parachutes can only do so much in the tenuous atmosphere, reached the ground still travelling at an estimated 126 km/h. Hence while the conical backshell appears to have burst apart on impact.

The Mars 2020 mission backshell and supersonic parachute seen from Ingenuity as it traverses over the debris zone, April 19th, 2022. The black object, slight above centre on the left edge of the image is actually part of one of Ingenuity’s landing feet, not part of the backshell debris. This image has also been post-processed to give near-Earth normal lighting and colour definition. Credit: NASA/JPL

Imagining the backshell and parachute not only provides some stunning photographs, it also helps inform engineers on how well the hardware actually worked, and offer insights to help with upcoming missions – such as the Mars Sample Return mission, for which initial testing of elements of the EDL systems recently started.

Getting the images proved a fitting celebration for the first anniversary of Ingenuity’s maiden flight. Stating at 11:37 local time, with the Sun ideally placed to offer the best lighting, the 159-second flight saw the helicopter climb to a height of 8 metres before flying 192 metres to take its first image. It then moved diagonally across the debris zone, hovering to take a further nine images at pre-determined points. It then moved 75 metres clear of the debris field and landed, for a total flight distance of 360 metres, With the flight completed, Ingenuity had clocked up a total of 49 minutes flying time on Mars, with a total distance covered of 6.2 km.

A further view of the Mars 2020 mission backshell and supersonic parachute seen from Ingenuity on April 19th, 2022., seen under Mars daylight lighting. Credit: NASA/JPL

The images reveal the backshell survived its impact surprisingly well, and that its protective white covering also came through entry into the Martian atmosphere with very little heat scarring, while many of the 80 high-strength suspension lines connecting it to the supersonic parachute are visible and appear intact.

Only around one-third of the 21.5 metre diameter parachute is visible, however. Whilst smothered in surface dust, the ‘chute appears completely undamaged by the supersonic airflow during inflation, and it is thought that only a third can be seen because of the way in which it collapsed onto itself after the backshell impacted.

Perseverance had the best-documented Mars landing in history, with cameras showing everything from parachute inflation to touchdown. But Ingenuity’s images offer a different vantage point. If they either reinforce that our systems worked as we think they worked or provide even one dataset of engineering information we can use for Mars Sample Return planning, it will be amazing. And if not, the pictures are still phenomenal and inspiring.

– Ian Clark, Mars Sample Return Ascent Phase Lead

JWST Update

The James Webb Space Telescope has now completed all aspects of aligning the 18 segments of its massive primary mirror and is moving into the final phase of science instrument commissioning.

As I’ve previously reported in these pages, JWST, the most ambitious space telescope yet built, is located at the Earth-Sun L2 position, 1.5 million kilometres beyond the orbit of Earth relative to the Sun. In March the core work of aligning the 18 segments of the primary mirror was completed such that the telescope could capture crystal clear images in the infra-red directly through its optical systems.

However, and  as I noted at the time, the process of commissioning the science instruments on the telescope would likely require further adjustments to ensure the everything is correctly aligned for science image processing. This work was the first formal step taken in the commissioning process for the science instrument suite once it had been powered up and had reached its required operating temperature range, and on April 28th, NASA confirm the month-long process of very fine final adjustments had been successfully completed, and the science team is now ready to move forward into the final phase of JWST’s commissioning: calibrating the instruments.

The optical performance of the telescope continues to be better than the engineering team’s most optimistic predictions. Webb’s mirrors are now directing fully focused light collected from space down into each instrument, and each instrument is successfully capturing images with the light being delivered to them. The image quality delivered to all instruments is “diffraction-limited,” meaning that the fineness of detail that can be seen is as good as physically possible given the size of the telescope. From this point forward the only changes to the mirrors will be very small, periodic adjustments to the primary mirror segment.

– NASA JWST press release, April 28th, 2022

This NASA image contains images from each of the major instruments on the James Web Space Telescope (JWST) to ensure the telescope’s mirrors are correctly aligned to allow all instruments to product perfect images. Credit: NASA/STScI
The completion of the alignment work came with the release of a set of images from each of the telescope’s science instruments, as shown above. These instruments are:

  • The Near Infrared Camera (NIRCam): the primary imager covering the infra-red wavelength range 0.6 to 5 microns. It is capable of detecting light from the earliest stars and galaxies in the process of formation, star populations in nearby galaxies, the light from young stars in our own galaxy, and objects within the Kuiper Belt.
  • The Near InfraRed Spectrograph (NIRSpec): primarily designed by the European Space Agency (ESA) NIRSpec will operate in tandem with NIRCam over the 0.6 to 5 micron wavelengths to reveal the physical properties of objects emitting light at those wavelengths.
  • The Mid-Infrared Instrument (MIRI): also primarily the work ESA, MIRI has both a camera and a spectrograph operating in the 5 to 28 micron wavelengths – longer than our eyes see. As such, it will be able to “see” and reveal the properties of near and distant objects “invisible” to NIRCam and NIRSpec.
  • FGS/NIRISS: technically two instruments supplied by the Canadian Space Agency operating in the 0.8 to 5.0 micron wavelengths:
    • The Fine Guidance Sensor (FGS): allows Webb to point precisely, so that it can obtain high-quality images.
    • The Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument: designed for first light detection, exoplanet detection and characterisation, and exoplanet transit spectroscopy

The final work in calibrating these instruments is expected to take around a month to complete, and will also involve ordering the telescope to point to different deep space targets so that the amount of solar radiation striking its heat shield will vary, allowing the science team to confirm that the thermal stability for the instruments and mirrors is being maintained within the optimal operating temperatures.

A comparison in resolution power between the Spitzer infra-red telescope (2003-2020) and JWST (2022), using the same region of deep space. NASA/STScI / 

As a part of the alignment exercises, JWST was directed to image an area of space that had been used for aligning / calibrating the mirrors and instruments used on the Spitzer Space Telescope (2003-2020). While a direct comparison between Spitzer (with a primary mission diameter of just 85 cm), and JWST (with a primary mirror diameter of 6.5 metres) is little on the “apples and pears” scale, putting the two commissioning images side-by-side does reveal just how much more of the universe JWST will be able to reveal to us.

Continue reading “Space Sunday: aerial views, infra-red images & a few notes”

Space Sunday: Ax-1 Artemis, ESA & a galaxy far, far, away

Crew Dragon Endeavour docked with the forward port on the US Harmony module at the ISS, and bearing the Axiom logo. Credit: NASA

The first entirely private sector mission to the International Space Station (ISS) lifted-off from the SpaceX Falcon launch facilities at Pad 39A, Kennedy Space Centre (KSC) on Friday April 8th, 2022, carrying a crew of four to the station aboard the Crew Dragon vehicle Endeavour.

The launch took place at 16:17 UTC, with the Falcon 9’s first stage making a flawless ascent prior to upper stage separation, then completing a boost-back manoeuvre and a successful return to Earth to land on one of the SpaceX autonomous drone ships. It marked the 5th successful flight for the core stage, which coincidentally was the same stage that launched the first all-private mission to Earth orbit – Inspiration4 (see: Space Sunday: Inspiration4 and Chinese flights) in September 2021.

Ax-1 has been seen by some as just another jolly jaunt into space by those who can afford it; however and in fairness, it is slightly more than that. Axiom Space was founded to create the world’s first commercial space station. While others have since entered this arena, Axiom has been granted access to the forward port of the ISS’ Harmony module, to which Axiom plans to dock the Axiom Orbital Segment; a complex that could grow to five pressurised modules after 2024.

Axiom’s plans for their space station (click for full size). Credit; Axiom Space

In order to help finance their plans, Axiom plan to offer a series of fare-paying flights to the ISS, with the 8-10 day Ax-1 being the first. However as a part of these flights, those paying for seats will also help Axiom pave the way towards their goal in bringing their first module to the ISS in 2024 and carry out a suite of selected on-orbit studies and experiments.

Commanding the mission is Michael López-Alegría, who was one of NASA’s most experienced astronauts prior to retiring in 2012. He holds the US record for the most EVAs undertaken by a NASA astronaut (10 totalling 67 hours and 40 minutes) and is also (and quite separately) licensed to officiate at wedding ceremonies. In 2017, he joined Axiom Space as their director of Business Development, and allowing him to regain his space flight status. Joining him on the mission are US entrepreneur  Larry Connor, Israeli businessman and former fighter pilot Eytan Stibbe and Canadian philanthropist and businessman Mark Pathy, each of whom paid an estimated US $55 million to join the mission.

The Ax-1 crew: from left – Larry Connor Mark Pathy Michael López-Alegría and Mark Pathy. Credit: Axiom Space / SpaceX
Endeavour took a gentle path up to the space station over a 20 hour flight; however, docking was delayed by some 45 minutes due to an issue with the video system used by the ISS crew to monitor docking operations.

Following post-docking checks, the hatches between Endeavour and the ISS were opened, and the Ax-1 team were welcomed aboard the station by the 7-person crew. During a brief ceremony-come-video press briefing, López-Alegría – who had become the first former astronaut to return to the ISS – presented his three fellow crew members with astronaut pins. Whilst not official US astronaut pins, those presented to Stibbe, Connors and Pathy have been designed by the Association of Space Explorers, which encompasses a lot of members from 38 different countries that have flown astronauts.

Alongside of their work in support of Axiom Space, the Ax-1 crew will take part in a multi-discipline science programme of some 25 different research experiments sponsored by the ISS U.S. National Laboratory in collaboration with the Mayo Clinic, the Cleveland Clinic, Canadian Space Agency, Montreal Children’s Hospital, Ramon Foundation (named for Ilan Ramon, the Israeli astronaut killed in the Space Shuttle Columbia disaster of 2003) and Israel Space Agency.

The Axiom Ax-1 crew (to the rear) with their ISS colleagues, around them in the foreground – counter-clockwise from right: NASA astronaut Tom Marshburn (holding the microphone) ; Roscosmos cosmonaut Oleg Artemyev (in the blue, centre); NASA astronaut Kayla Barron; cosmonauts Sergey Korsakov and Denis Matveev (floating); and upside down NASA astronauts Raja Chari and ESA astronaut Matthias Maurer. Credit: NASA

As a fully private mission to the ISS, Ax-1 not only features a non-government crew launched aboard a private sector space vehicle and rocket, it is also being managed through the SpaceX flight control centre, Hawthorne, California and Axiom’s own mission control centre in Houston, Texas.

Artemis WDR: Further Issues and Delay

The Wet Dress Rehearsal for the Artemis 1 Space Launch System (SLS) vehicle at KSC’s Pad 39B continues to hit niggling problems, with a resumption of testing now pushed back until April 12th.

As I noted in my previous Space Sunday report, while it had been hoped this full test of a launch countdown procedure, including fuelling the massive rocket’s liquid propellant tanks, could be completed in a 3-day period between April 1st and April 3rd, the test ran into a series of issues that caused efforts to be scrubbed on two occasions.

The issues were now with the rocket itself, which performed flawless during the tests up until the scrubs were each called, but with support systems within the vehicle’s mobile launch tower. However, after the second set of issues on April 3rd caused a scrub, the plan had been to investigate and correct the issue in time to resume the countdown on April 4th and complete the tests ahead of the launch of the SpaceX / Axiom Ax-1 mission reported above – a launch that had already been postponed from April 3rd.

Artemis 1 and its mobile launch platform on Pad 39B at Kennedy Space Centre. Credit: NASA

As the investigations took longer than planned, on April 4th, the decision was taken to stand down WDR operations to allow the Ax-1 to go ahead, and to resume the tests on April 9th. But on April 7th, during a check on the rocket’s systems, engineers found a problem when trying to maintain helium purge pressure in the Interim Cryogenic Propulsion Stage (ICPS), the upper stage of the rocket itself.

The ICPS is based on the second stage of the Delta 4 launch vehicle. It uses a single RL10 engine to propelled the payload carrying section of the rocket – although it will be replaced by the more powerful and purpose-built Exploration Upper Stage from the third SLS flight (Artemis 4) onwards. This particular ICPS was one of the first to be completed, and had been in storage for several years awaiting the completion of the Artemis 1 core stage and boosters.

The Artemis 1 ICPS at Kennedy Space Centre, prior to its integration with the rest of the SLS rocket. Credit: NASA

The issue was traced to a check valve intended to prevent helium – used to purge propellant lines and drain propellant – from escaping the rocket., the valve failing to function as intended. To allow time for a possible fix for the problem to be developed and attempted, the decision was taken to push test resumption by to April 12th. Unfortunately, by April 9th, it became clear that the valve would need to be replaced; but rather than cancel the WDR completely, NASA has decided to complete the test as planned on the 12th – but to only perform a “minimum fill” of the ICPS tanks;  enough to prove the propellant loading system works. This, with a full load of the core stage tanks is seen as sufficient for the WDR to be completed.

Replacing the check valve will be carried out once the rocket has been returned to KSC’s Vehicle Assembly Building as a part of the post-WDR checks. However, this means that any chance of Artemis 1 making the hoped-for May launch window is now out of the question, whilst NASA is confident replacing the valve will correct the issue, it is also unlikely the turn-around can be completed in time for the rocket to make the June 6th through 16th launch window, potentially making July the earliest Artemis 1 launch opportunity.

Continue reading “Space Sunday: Ax-1 Artemis, ESA & a galaxy far, far, away”

Space Sunday: distant stars, sounds on Mars, a return and a rocket

The Artemis 1 Space Launch System (SLS) rocket stands on its mobile launch platform at Kennedy Space Centre’s Pad 39B, where it is undergoing a full wet dress rehearsal ahead of its launch later this year – see later in this article for more. Credit: NASA

The Furthest Star

My previous Space Sunday update ended with a note that NASA would be making an announcement at the end of March 2022 concerning a new discovery by the Hubble Space Telescope (HST) that could have repercussions for the James Webb Space Telescope (JWST), once it commences its scientific mission. Announced on March 30th, that discovery was revealed to be the imaging of the most distant individual star from Earth yet discovered. So distant, in fact, that it has taken the light from it 12.9 billion years to reach us. By contrast, the next oldest individual star we have detected using Hubble was born when the universe was already some 4 billion years old, taking 9 billion years to reach us.

Christened  Eärendel, the Old English term for “morning star” (and, as Tolkien fans like me will know, was the name initially given to the half-human, half-elven navigator, prior to Tolkien changing the name of that character to Earendil), the star was discovered as a part of a HST programme called RELICS -the REionisation LensIng Cluster Survey, intended to capture to light from really far distant objects born not long after the Big Bang.

To do this, RELICS employs the phenomenon of gravitational lensing, whereby the mass of a huge object such as a galaxy or cluster of galaxies bend and focuses the light coming from objects far beyond them, allowing us to see them as magnified, arc-like objects. In this case, a cluster of galaxies called WHL0137-08 was found to be lensing the light of a galaxy far beyond them, drawing the collected light of that galaxy out into a slender crescent Hubble could see and which astronomers nicknamed the Sunrise Arc.

The red arc of the Sunrise Arc galaxy, and within it, the single point of light of Eärendel. Credit: NASA, ESA, Brian Welch (JHU), Dan Coe (STScI)

For the most part, the Sunrise Arc is blurred and instinct, like sunlight diffracted by the ripples on the surface of a swimming pool cast blurred clouds of light on the bottom of the pool. However, by coincidence, at the time the images of the Arc were recorded, Eärendel appeared directly on, or extremely close to, a curve in space-time that provided maximum brightening, allowing its light to stand out as an individual point within the blurriness of the Sunrise Arc – just like some rays of light can strike the surface of a swimming pool at precisely the right moment to avoid diffraction by the surface ripples and form pinpoints of light on the bottom of the pool rather than being blurred.

Initially it was thought that the star might in fact be a cluster, rather than a lone star, but careful analysis of Eärendel ‘s red shift has swayed astronomers towards believing it is most likely just the one star (although the potential for it to be a binary system hasn’t been entirely ruled out) of enormous size at least 50 times the mass of the Sun and correspondingly enormous luminosity.

Such is Eärendel age, that it at the time its light departed it, the star was likely only made up of primordial hydrogen and helium following the Big Bang. This makes it a prime target for study by JWST – which thanks to is infra-red capability can pick out more information about a target object than HST -, as doing so could reveal more about the state of the early universe and early stellar development.

However, such is the nature of things that – whilst referring to the star in the present tense, it’s important to note that it is very likely that while the most distant individual star observed by HST, Eärendel is not the oldest star yet found; in fact, it probably no longer exists. This is because such supermassive stars tend to burn through their available fuel stocks in mere millions of years, rather than billions. It’s therefore very likely that at some point when the light captured by Hubble was still making its way towards us, Eärendel either violently exploded into a supernova, or collapsed into a black hole – something we’ll only know for sure a few million years into our future.

The Nature of Sound on Mars

We’re all familiar with the concept of the speed of sound. Here on Earth and at sea level, with the temperature at 20ºC, sound travels at 343 metres per second (m/s). However, that is not an absolute; it varies according to the relative atmospheric temperature and density. At altitudes up to 20 km, the speed of sound slowly declines due to the thinning of the atmosphere; however, above 20 km, whilst the atmosphere continues to thin, its temperature actually increases, making it more excitable, and so the speed of sound increases once more.

Much the same was thought to be true on Mars, where the relatively thin atmospheric density close to the surface of the planet was thought to limit sound waves to around an average of 240 m/s (again, allowing for variations in temperature).  However, what no-one expected was that the speed of sound would vary according to frequency – but that is what the Mars 2020 mission has revealed.

An international team of scientists reached this conclusion after analysing recordings made by one of two microphones mounted on the Perseverance rover. The SuperCam microphone mounted at the top of the rover’s mast is somewhat directional in nature in that turning / tilting the SuperCam unit allows the microphone to be pointed directly at sound sources, allowing it to record them with a good level of fidelity.

The Mars 2020 rover’s SuperCam system with the “directional” microphone highlighted. Credit: NASA/JPL

This is been done a number of time during the rover’s mission. For example, the camera has been pointed towards the Ingenuity Mars helicopter, allowing it to directly record the low-frequency beating of the helicopter’s rotors. It is also naturally pointing at rockets targeted for “zapping” by SuperCam’s laser. It has also been able to listen to tools and equipment operating at the end of the rover’s robot arm. All of these sounds have now been collectively analysed, and scientist have been surprised to find that while lower frequency sounds – such as the beating of Ingenuity’s rotors – travel at the expected Martian average of 240 m/s, sounds at frequencies greater then 240 Hertz, such as the higher-pitched click-click-clicking of the SuperCam laser actually travel around 10 m/s faster – the first time this has ever been observed.

The cause for this unusual difference is thought to be the result of the Martian atmosphere being largely carbon-dioxide. In studying the tenuous Martian atmosphere, scientists have discovered during the day, the heat of the Sun, deflected as it is by the surface of the planet, generates an unusual turbulence in the first 10 km of atmosphere above the planet. This turbulence has an unusual impact on the carbon dioxide that isn’t seen in Earth’s denser atmosphere: it allows higher frequency sounds to excite the carbon dioxide molecules a lot more than low-frequency sounds, allowing such higher frequencies to be more rapidly transmitted through the atmospheric medium.

Because this effect happens almost smack in the middle of the bandwidth of sounds audible to the human ear, it means that if we were able to stand out in the open on Mars and listen to something like a symphony being played a few 10 of metres away, rather than hearing all the notes collectively as we would on Earth, we’d hear the higher notes a second or so ahead of the lower notes, resulting in a discordant mess. However, a more practical outcome of this discovery is that engineers believe that by listening to the different frequencies within the sounds made by various pieces of audible equipment on the rover, they could potentially identify if that part of the rover is experiencing issues, and thus be forewarned that action might be required well before a potential failure occurs.

Continue reading “Space Sunday: distant stars, sounds on Mars, a return and a rocket”

Space Sunday: a big rocket, a telescope & yellow and blue

Artemis 1: the SLS rolls slowly out of the Vehicle Assembly Building (VAB) and out to pad 39B at Kennedy Space Centre. Credit: NASA / Artemis- 

NASA has rolled out the first of what is intended to be both the first of its new “super rocket”, the Space Launch System, and the vehicle to start the United States and its international partners on the road back to the Moon.

At 21:47 UTC on March 17th, the huge rocket, mounted on its mobile launch platform, slowly crept out of one of the high bays of the Vehicle Assembly Building (VAB), the iconic cube sitting within NASA’s Kennedy Space Centre which was used as an integral part of Project Apollo and which is now fulfilling a similar role for Project Artemis, on the back of a massive crawler-transporter at the start of a 6.72 km journey to Kennedy Space Centre’s Lunch Complex pad 39B.

It was not a swift journey, taking some 11 hours to complete  – albeit with stops along the way for checks to be carried out – the crawler-transporter finally reaching the top of the incline of the launch pad 04:15 UTC on Friday, March 18th.

The move of the rocket from VAB to pad was not in readiness for the launch of Artemis 1 – the mission this SLS vehicle will carry to orbit – but rather for the final series of tests to be carried out on the fully integrated rocket and its Orion Multi-Purpose Crew Vehicle (MPCV) payload to ensure both are ready for that launch, which is currently set for a provisional window in mid-May 2022.

Another view of Artemis 1 SLS emerging on its mobile launch platform from the VAB at Kennedy Space Centre. Credit: NASA / Artemis 1

As I noted in my last Space Sunday update, the focus of these tests will be a full wet dress rehearsal, due to take place in April. This will see the rocket fully fuelled and go through a full launch countdown that will stop just nine seconds prior to an actual launch. The intention is to make sure everything with the rocket, the payload and the launch systems are all ready for a launch attempt, and will be followed by a further 8-9 days of additional pad tests. After this, the rocket will be returned to the VAB and assessed ready for final flight clearance.

When it does take flight, SLS will become the most powerful launch system built by NASA. The Block 1 vehicle being capable of delivering up to 95 tonnes to low Earth orbit, and the upcoming Block 1B up to 105 tonnes, and the future Block 2 vehicle up to 130 tonnes – putting it in the same lifting class as SpaceX’s Starship / Super Heavy launch system, but potentially far more flexible in turns of specialised launches, SLS being capable of launching smaller payloads (e.g. 23-45 tonnes, depending on the launcher variant) directly to the Moon, or other payloads out into the solar system without any need for on-orbit refuelling.

However, as I’ve noted before, there are some significant cost issues for SLS that may impact its use, the most notable being that of ongoing costs. Development work on the SLS system has thus far eaten US $23.01 billion, and while NASA would claim a lot of that (US $14 billion) has gone directly into work creation, it nevertheless means that as a non-reusable system, SLS is terribly expensive: NASA’s own Office of Inspector General (OIG) estimates each launch will cost some US $4 billion, twice NASA’s launch cost estimate, and will never fall below US $1 billion as the agency has suggested.

This cost factor has already seen NASA turn to other launch systems for missions originally earmarked for SLS. The Europa Clipper mission, for example, has been move to a SpaceX Falcon Heavy launcher on the ground of launch costs (and the fact that SLS generates so much vibration at launch, it is unsuitable to fly certain sensitive instruments into space).

As it is, five SLS missions in support for Artemis have thus far been confirm, with vehicles for three more after Artemis 1 already under construction:

  • Artemis 1: uncrewed mission to cislunar space to test the Orion MPCV; duration: some 25.5 days – mid 2022.
  • Artemis 2: crewed mission to lunar orbit; duration: 10 days – 2024.
  • Artemis 3: crewed lunar obit / lunar landing mission; duration:30 days – 2025/26:
  • Artemis 4: crewed mission to a lunar near-rectilinear halo orbit (NRHO) in support of the Lunar Gateway station and the core I-HAB deployment – 2026/27
  • Artemis 5: crewed mission to a lunar near-rectilinear halo orbit(NRHO) in support of the Lunar Gateway station and the European System Providing Refuelling, Infrastructure and Telecommunications (ESPRIT) module, together with a lunar surface mission – 2027-28.

Starship HLS: NASA Updates

A further key component for Project Artemis is the Human Landing System (HLS), the vehicle that will be used to transfer crews between lunar orbit and the surface of the Moon and (initially) provide them with living space whilst on the Moon. Currently, only one contract has been issued for HLS, and as I’ve noted before, it is to SpaceX for the use of a lunar variant of their Starship vehicle, although the agency has more recently been order to acquire HLS vehicles from other sources.

As a part of their Artemis HLS update, NASA provides images of astronauts working with prototype elements that will be used within the vehicle, which SpaceX are due to build. Credit: NASA

Coinciding with the SLS roll-out at Kennedy Space Centre, NASA issued an update on the SpaceX HLS programme, including the work going into some key elements, such as the elevator that will carry the 2-person crew of Artemis 3 the 30-40 metres down the side of the vehicle to the Moon’s surface and back after landing, together with the airlock through which they’ll leave / enter HLS during surface operations and some of the living / working facilities inside the vehicle.

The update also confirms that HLS will require some six starship / super heavy launches:

  • The launch of a special “tanker” Starship that will be parked in Earth orbit and used for a wide range of Starship propellant transfer operations.
  • Four further launches of re-usable Starship vehicles equipped with additional fuel tanks that will carry propellants to be transferred to the orbital “tanker”.
  • The HLS starship itself and the cargo needed for Artemis 3. This will dock with the “tanker” and take fuel from it that can be used to boost the HLS vehicle to lunar orbit and to both land it on the Moon and then get it back to lunar orbit.
Artemis 3 / HLS operations concept graphic. Credit: NASA

Once the HLS is in lunar orbit, the 4-person Artemis 3 crew will then launch to the Moon aboard an Orion MPCV lifted by SLS, and rendezvous with HLS so two can transfer to it and then travel to / from the lunar south pole. After transferring back to Orion, the crew will return to Earth, leaving the HLS starship in lunar orbit, potentially with either fuel to be used by the crew of Artemis 5, the second lunar landing mission.

However, whilst SpaceX HLS is earmarked for this mission (and will likely be the only HLS craft capable of supporting Artemis 5 in 2027/28), some in Congress are pushing NASA to use an alternative HLS design for the second lunar landing (which is which Artemis 4 was switched from a join lunar gateway / lunar landing mission to being solely a lunar gateway mission.

Continue reading “Space Sunday: a big rocket, a telescope & yellow and blue”

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”