Space Sunday: the mathematician of NASA

Tribute to Katherine Johnson. Credit: Breen, San Diego Union-Tribune

So often, when we think of the early years of US space flight, we think of steely-eyed, square-jawed test pilots supported in their missions by male, bespectacled and white-shirted scientists and flight controllers, their breast pockets lined with pens of various colours, all with similar haircuts and staring earnestly at computer screens, headsets allowing them to talk in clipped, precise terms with one another in acronym-laden sentences.

While both were very much the public persona for NASA, even becoming something of a cliché in television and film, they were only in fact the tip of the iceberg of the multitude of talents that formed NASA and made its missions possible. In particular, the image of the “nerds” of mission control has tended to very much overshadow the role played by many women in getting America both into orbit and to the Moon.

One of the foremost of these women was Creola Katherine Coleman, better known as Katherine Johnson, who sadly passed away on February 24th, 2020 at the age of 101. As a mathematician who spent 35 years working for NASA and its precursor, her calculations of orbital mechanics were critical to the success of the first US flights into space during the Mercury programme, and her work also encompassed the Apollo programme and the space shuttle.

Katherine Johnson, circa 1960. Credit NASA

Katherine Johnson was born on August 26, 1918, in White Sulphur Springs, West Virginia, the youngest of four children born to Joylette Coleman, a teacher, and her husband Joshua Coleman, a lumberman, farmer, and handyman. She showed a natural ability with mathematics from an early age. However, as her home county of Greenbrier did not offer public schooling for African-American students past the eighth grade (13-14 years of age), her parents enrolled her, at the age of 10, at the high school on the campus of West Virginia State College.

Following her graduation at 14, she attended West Virginia State, where she took every course in mathematics offered by the college and studied under chemist and mathematician Angie Turner King, and William Schieffelin Claytor, the third African-American to receive a Ph.D. in mathematics In fact, Claytor was so impressed with Johnson, he added new courses just for Katherine. Graduating summa cum laude in 1937 at the age of 18 and with degrees in mathematics and French, Johnson took on a teaching job at a black public school in Marion, Virginia.

She returned to studying mathematics after marrying her first husband, James Goble in 1939, becoming the first African-American woman to attend graduate school at West Virginia University.

Johnson’s association with aerospace commenced in 1953 when she joined the National Advisory Committee for Aeronautics (NACA), joining the Guidance and Navigation Department at the Langley Memorial Aeronautical Laboratory, Virginia. Here, she initially worked in a team of women supervised by mathematician Dorothy Vaughan, carrying out a range of mathematical analyses of aircraft flight dynamics, wind handling and more. She was then reassigned to the Guidance and Control Division of Langley’s Flight Research Division.

At first she [Johnson] worked in a pool of women performing maths calculations. Katherine has referred to the women in the pool as virtual “computers who wore skirts”. Their main job was to read the data from the black boxes of planes and carry out other precise mathematical tasks. Then one day, Katherine (and a colleague) were temporarily assigned to help the all-male flight research team. Katherine’s knowledge of analytic geometry helped make quick allies of male bosses and colleagues to the extent that, “they forgot to return me to the pool”. While the racial and gender barriers were always there, Katherine says she ignored them. Katherine was assertive, asking to be included in editorial meetings (where no women had gone before). She simply told people she had done the work and that she belonged.

– Oral history archive at by the US National Visionary Leadership Project

Katherine G. Johnson Computational Research Facility, Langley Research Centre, Virginia, inaugurated in 2019 and named in honour of Katherine Johnson. Credit: NASA

With the formation of NASA, Johnson worked as an aerospace technologist, moving to the agency’s Spacecraft Controls Branch, a department in which she continued to work through until her retirement from the agency in 1986. Her first major project was calculating the launch window and flight trajectory for Freedom 7, the sub-orbital flight that made Alan Shepard the first American in space on May 5th, 1961. In particular, her trajectory calculations – manually produced – ensured the recovery teams were on hand when Shepherd splashed down. In addition, to her calculation for flights, Johnson plotted backup navigation charts for the astronauts in case of electronic failures aboard their craft.

Such was her reputation and prowess, Johnson was key to ensuring NASA could transition from human computers to electronic computers. In this role, when John Glenn was preparing to make NASA’s first orbital flight around the Earth, he refused to fly unless and until Johnson had personally verified all of the electronic flight calculations for the mission. Despite the greater complexity in orbital flight calculations, Johnson did so by comparing the electronically-produced calculations  with her own manual calculations that she produced over the course of a day and a half – a feat that passed almost unnoticed in the pages of history.

In this respect, Johnson – although living in a state where segregation on the basis of colour was still very real (despite NASA’s somewhat more relaxed view of things) – would later state that she found sexism in the workplace the bigger problem (Glenn, for example, called for her to review the data relating to his flight simply as “the girl”).

We needed to be assertive as women in those days – assertive and aggressive – and the degree to which we had to be that way depended on where you were. I had to be. In the early days of NASA women were not allowed to put their names on the reports – no woman in my division had had her name on a report. I was working with Ted Skopinski and he wanted to leave and go to Houston … but Henry Pearson, our supervisor – he was not a fan of women – kept pushing him to finish the report we were working on. Finally, Ted told him, “Katherine should finish the report, she’s done most of the work anyway.” So Ted left Pearson with no choice; I finished the report and my name went on it, and that was the first time a woman in our division had her name on something.

– Katherine Johnson quoted in Black Women Scientists in the United States, 1999.

President Barack Obama awards the Presidential Medal of Freedom to Katherine Johnson in 2015. Credit: UPI

As NASA shifted gears to achieve President Kennedy’s goal of “landing a man on the Moon and returning him safely to the Earth”, Johnson threw herself into the task of making sure it could happen. She would arrive at the office early in the morning, work through until late in the afternoon, then go home to look after her three daughters – born to her late first husband, and living with her and her second husband, James Johnson – then returning to NASA after the children were in bed, maintaining a schedule of 14- to 16-hour days.

These hours enabled her to carry out a critical role in calculating Apollo 11’s flight to the Moon and back and – most crucially of all – she calculated the exact time that the lunar module ascent stage needed to lift-off from the lunar surface in order to successfully rendezvous with the Command and Service Module, a feat she would come to regard as her proudest accomplishment.

During this time, she also embarked on co-authoring a series of papers specifically for the Apollo programme (as part of some 26 science and mathematics papers she wrote while at the agency). These were intended to guide mission teams and astronauts alike through scenarios in which various computer systems on the spacecraft might fail. One of these papers, produced in 1967 with Al Hamer, detailed alternative methods of celestial navigation in the event of a failure with Apollo’s on-board navigation systems, and was pulled into use in the Apollo13 rescue in April 1970.

Everybody [in the Apollo programme] was concerned about them getting there. We were concerned about them getting back.

– Katherine Johnson, 2010, discussing her co-authored approach to one-star navigation,
tested by Jim Lovell during Apollo 8 (1968), and which formed a part of the Apollo 13 recovery efforts (1970)

Following Apollo, Johnson moved to the space shuttle programme, again playing a key role in preparations for the 1981 first flight of the original space-capable orbiter vehicle, Columbia, and worked on orbital requirements for the Earth Resources Technology Satellite (ERTS) project, which would later be renamed Landsat. Additionally, in leading up to her retirement in 1986, she turned her mind to plans for missions to Mars.

Following her official retirement, Johnson spent her later years encouraging students to enter the fields of science, technology, engineering, and mathematics (STEM), talking about her work at NASA and remaining a strong advocate of human space flight. In 2015, she was awarded the Presidential Medal of Freedom by President Barack Obama, while in 2016 her work, and that of her fellow African-American women at NASA was charted in the 2016 biographical movie Hidden Figures. In that same year NASA dedicated a purpose-built unit, the Katherine G. Johnson Computational Research Facility at the Langley Research Centre, in her honour. A second facility, also in Virginia, was renamed in her honour in 2019. The is responsible for developing and verifying software crucial to NASA missions. Both are fitting tributes to one of NASA’s pathfinders.

Katherine Johnson at 97. Credit: unknown

I found what I was looking for at Langley. This was what a research mathematician did. I went to work every day for 33 years happy. Never did I get up and say, “I don’t want to go to work.”

– Katherine Johnson, commenting on her time at NASA

Katherine Johnson died at a retirement home in Newport News on February 24, 2020, at age 101, she is survived by her three daughters, six grandchildren and 11 great-grandchildren. Her legacy is one that has carried humans into space and to the Moon, and paved the way for modern human space flight.

Space Sunday: moles, asteroids and a high speed planet

InSight’s scoop hovers over the HP3 mole. Credit: NASA / JPL

It’s now close to 15 months since NASA’s InSight lander arrived on Mars (see Space Sunday: insight on InSight for an overview of the mission and Space Sunday: InSight, MarCO and privately to the Moon for more on the mission and InSight’s Mars arrival). In that time the lander has completed a lot of science, but one thing has remained an issue: the HP³ experiment.

This is one of two surface experiments InSight placed on Mars, and comprises a base module and a long, slender self-propelled probe called the “mole”, designed to “burrow” its way down into the the sub-surface to a depth of up to 5 metres, towing a sensor-laden tether behind it designed to measure the heat flow from the planet’s interior. The mole has an internal hammering mechanism that is designed to drive it deeper into the ground, but this relies on friction against the material forming the walls of the hole it is creating – and this hasn’t been happening.

After a good initial start, the probe came to a halt with around 50% of its length embedded in the soil. At first it was thought it had hit solid bedrock preventing further motion; then it was thought that the mole was gaining insufficient traction from the hole walls, on account of the fine grain nature of the material it was trying to move through.

The HP3 “mole” showing the spring mechanism and “hammer” it drives into the ground. Credit: DLR

By mid-2019, engineers thought they had a solution: use the scoop at the end of the lander’s robot arm to compact the soil around the lip of hole in the hope of forcing sufficient material into the hole it would provide the traction the probe needed to drive itself forward. When this failed, the decision was made push the scoop directly against the side of the probe, pinning it between scoop and hole wall to again give the probe the traction it needed.

Initially, this approach worked, as I noted in Space Sunday: a mini-shuttle, Pluto’s far side & mole woes, but then the mole “bounced back”. Since then, the probe’s progress has been a case of “three steps forward, two steps back”, making some progress into the ground and then bouncing back – a source of much frustration among the science team.

After a year with the mole more-or-less “stalled”, mission engineers have decided to take more direct action. The decision has been made to try to “push” the probe using the robot arm’s scoop. This means placing the scoop on the top end of the mole – an approach that has so far been avoided out of concerns to might damage the sensor tether as it emerges from the same end of the probe. However, in manipulating the lander’s robot arm and its scoop over the course of a year, engineers are confident they can avoid harming the tether.

This latest effort to get the mole into the surface will take place in late February / early March. If it is successful, the team may revert to using the scoop to once again compress the sides of the probe’s hole to try to provide it with further traction as it continues to dig down into the subsurface material. Should the attempts fail, it’s unclear what might be tried to get the mole moving again; the mission team admitting they have “few alternatives” left to try.

How to Deflect an Asteroid

On April 13, 2029, an asteroid in the region of 370 metres in length and 45 metres across will pass by Earth at 30 km/s no further away from the planet’s surface than some of our geostationary satellites.

Called 99942 Apophis, an object I’ve written about in past Space Sunday articles, it is one of a large number of potentially hazardous objects – asteroids larger than 140 m in length that in crossing the Earth’s orbit as both they and the planet go around the Sun, pose a potential risk of one day colliding with us, with potentially devastating consequences. When it was   discovered in 2004, initial tracking of Apophis suggested it could collide with Earth in 2029. Further observations of the object showed this would not happen, not would it do so the next times it passes close to Earth in 2036, 2068 and 2082.

Extinction level event: a very large asteroid impact. Credit: Anselmo La Manna/YouTube screenshot

Which is not to say Apophis or 101955 Bennu, or one of the many other PHOs – Potentially Hazardous Objects – that are being tracked might one day strike Earth. The tipping point for such a collision comes down to such an object passing through, or close to, it’s gravitational keyhole. This is a tiny region of space – perhaps only 800 metres across – where gravitational influences – notably that of Earth – are sufficient to actual “pull” an objects course onto a collision with Earth.

Currently, plans to try to prevent such an impact revolve around identifying when an object has passed its particular keyhole, making an collision inevitable. There’s a reason for this: identifying where an objects keyhole might lie isn’t a precise science, and relies on scientists known an awful lot, including things like the size, mass, velocity and composition of these objects, what forces might be at work to influence their orbit, and so on. However, by leaving things until after an object has passed its keyhole means the time available to try to divert it is relatively short, perhaps months or just a couple of years or so, leaving very little time to plan and execute a mission to prevent any such collision.

Better then, to identify when an object is liable to pass close enough to its keyhole that it it will be drawn into a collision path. This would provide a far greater lead time for planning how to deal with it. This is exactly what a team of MIT researchers are suggesting in a part that also defines a framework for deciding which type of mission would be most successful in deflecting an incoming asteroid.

Continue reading “Space Sunday: moles, asteroids and a high speed planet”

Space Sunday: A pale blue dot, and more on Betelgeuse

A pale blue dot: Earth – the bright dot just right-of-centre – as seen from a distance of 6 billion km (40.5 AU). Credit: NASA / Kevin Gill et al

Thirty years ago, in February 1990, the Voyager 1 space craft had completed its primary mission and was about to shut down its imaging system. However, before it did so, and in response to lobbying from the late Carl Sagan, celebrated astronomer, teacher, broadcaster, writer, futurist and member of the Voyager programme’s imaging team, mission managers order the spacecraft to turn its imaging system back towards Earth to take a final photograph of its former home.

Captured on February 14th, 1990, the image revealed Earth as little more than a tiny blue pixel caught in a  streak of sunlight falling across the camera’s lens. Sagan immediately dubbed the image Pale Blue Dot, and it became his – and Voyager 1’s – Valentine’s Day gift to all of humanity; a last goodbye from the probe taken at a distance of 6 billion km (40.5 AU); 34 minutes later, its camera system was permanently powered down to conserve the vehicle’s power generation system.

From the moment it was published, the image became iconic: a representation of the sum total of humanity, something Sagan recognised at a time when the Cold War still dominated world politics.

Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilisation, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every ‘superstar,’ every ‘supreme leader,’ every saint and sinner in the history of our species lived there–on a mote of dust suspended in a sunbeam.

…It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.

– Carl Sagan, Pale Blue Dot, 1994

To mark the 30th anniversary of the original image, NASA issued a newly enhanced version of the image, carefully processed by a team led by software engineer and imagining specialist, Kevin M. Gill, seen at the top of this article. It once again reveals just how small and lonely our world really is. And while the Cold War has long since past, in this age of global warming and climate change, this new image of that tiny, pale blue dot and Sagan’s words remain as powerful a reminder of our fragile place in the Cosmos as they did more than two decades ago.

Betelgeuse: Extent of Dimming Revealed

I’ve previously written about the dimming of Betelgeuseas seen from Earth on a couple of occasions over the past few months (see: Space Sunday: a look at Betelgeuse (December 2019) and A farewell to Spitzer, capsules, stars and space planes (January 2020)). Now two images and a video have been released to show just how startling the apparent changes in the star have been over the course of a year.

As an irregular – and massive – variable star, Betelgeuse goes through cycles of dimming and brightening over time. However, what has occurred over the course of the past year is without precedent in the 125-year history of observations marking the star’s behaviour.

Overall, Betelgeuse’s apparently magnitude (brightness as seen from Earth) has fallen by a factor of 2.5 (or roughly 25-30%). This has prompted speculation that the star may have exploded into a supernova – its eventual fate – and we are currently seeing the light, which takes approximately 643 years to reach us, from the run-up to that cataclysmic event. While most astronomers do not believe this to be the case, the two images do present a stunning spectacle of a star in flux.

Side-by-side comparison of Betelgeuse’s dimming, as seen by the SPHERE instrument on ESO’s Very Large Telescope. Credit: ESO/M. Montargès et al.

The images were captured by the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument attached to the Very Large Telescope (VLT, currently the most advanced visible light telescope in the world) operated by the European Southern Observatory Captured in January and December 2019, they not only show just how much  Betelgeuse has dimmed in that time, but also how it seems to have changed its shape.

Again, such changes of shape aren’t unusual for a pulsating variable star like Betelgeuse. The surface of such a star tends to be made up of giant convective cells that move, shrink and swell. However, while these pulses – referred to as stellar activity – have likely been responsible for past changes in Betelgeuse’s shape observed from Earth, they have never been anywhere as extreme as those indicated by SPHERE – although it has been acknowledged that they could also be exaggerated by a cloud of dust ejected by the star long enough ago to have cooled, and is now partially obscuring our view of Betelgeuse.

Continue reading “Space Sunday: A pale blue dot, and more on Betelgeuse”

Space Sunday: solar studies and rocket tests

An artist’s impression of ESA Solar Orbiter over the Sun. Credit: ESA

At 04:03 UTC  on Monday, February 10th (23:03 EDT, USA), the European Space Agency’s Solar Orbiter is due to be launched atop a United Launch Alliance Atlas V from Cape Canaveral Air Force Station, Florida. Referred to as SolO, the mission is intended to perform detailed measurements of the inner heliosphere and nascent solar wind, and perform close observations of the polar regions of the Sun, which is difficult to do from Earth, in order to gain a much deeper understanding of the processes at work within and around the Sun that create the heliosphere and which give rise to space weather.

The launch will mark the start of a three 3-year journey that will use a fly-by of Earth and three of Venus to use their gravities to help shift the satellite into a polar orbit around the Sun. Once there, and at an average distance of some 41.6 million km, SolO will move at the same speed at which the Sun’s atmosphere rotates, allowing it to study specific regions of the solar atmosphere beyond the reach of NASA’s Parker Solar Probe and Earth observatories for long periods of time.

ESA’s Solar Orbiter, built by Airbus UK within its clean room assembly area. The large flat panel to the left is the craft’s Sun shield. Credit: ESA

Our understanding of space weather, its origin on the Sun, and its progression and threat to Earth, comes with critical gaps; the hope is by studying the the polar regions of the Sun’s heliosphere, scientists hope they can fill in some of these gaps. The outflow of this plasma interacts with the Earth’s magnetic field and can have a range of potential effects, including overloading transformers and causing power cuts, disrupting communications and can potentially damage satellites. Further, the disruption of the Earth’s magnetic fields can affect the ability of whales and some species of bird to navigate.

We don’t fully understand how space weather originates on the sun. In fact, events on the sun are very hard to predict right now, though they are observable after the fact. We can’t predict them with the accuracy that we really need. We hope that the connections that we’ll be making with Solar Orbiter will lay more of the groundwork needed to build a system that is able to predict space weather accurately.

– Jim Raines, an associate research scientist in climate and
space sciences engineering

Specific questions scientists hope SolO will help answer include:

  • How and where do the solar wind plasma and magnetic field originate in the corona?
  • How do solar transients drive heliospheric variability?
  • How do solar eruptions produce energetic particle radiation that fills the heliosphere?
  • How does the solar dynamo work and drive connections between the Sun and the heliosphere?

To do this, the satellite is equipped with a suite of 10 instruments, some of which will be used to track active solar regions that might explode into a coronal mass ejections (CMEs), a major driver of space weather. When a CME occurs, SolO will be able to track it and use other instruments to be able to break down the composition of the energetic outflow (and that of the outflowing solar wind in general).

Knowing the composition of this outflow should help determine where energy is being deposited and fed into the solar wind from eruptions on the Sun, and how particles are accelerated in the heliosphere – the bubble of space where the Sun is the dominant influence, protecting us from galactic cosmic radiation.

The Solar Orbiter mission. Credit: ESA

Combined with the work of the Parker Solar Probe, launched in August 2018 (see: Space Sunday: to touch the face of the Sun) and which gathers data from within the Sun’s corona, and observations from Earth-based observatories such as the Daniel K. Inouye Solar Telescope (DKIST), Solar Orbiter’s data should dramatically increase our understanding of the processes at work within and around the Sun.

Like the Parker Solar Probe, SolO will operate so close to the Sun it requires special protection – in this case a solar shield that will face temperatures averaging 5,000º C on one side, while keeping the vehicle and its equipment a cool 50º C less than a metre away on the other side. This shield is a complex “sandwich” starting with a Sun-facing series of titanium foil layers designed to reflect as much heat away from the craft as possible. Closest to the vehicle is a aluminium “radiator” that is designed to regulate the heat generated by the craft and its instruments. Between the two is a 25-cm gap containing a series of titanium “stars” connecting them into a single whole. This gap creates a heat convection flow, with the heat absorbed by the titanium layers venting through it, drawing the heat from the radiator with it, allowing Solar Orbiter to both expect excess solar heating and present itself from overheating.

SolO’s primary mission is due to last 7 years, and those wishing to see the launch can watch it livestreamed across a number of platforms, including You Tube.

Continue reading “Space Sunday: solar studies and rocket tests”

Space Sunday: telescopes, lunar plans and Voyager 2

An artist’s impression of the CHEOPS observatory. Credit: ESA

On January 29th, 2020, the latest mission to study planets beyond our own solar system opened its eye to take a first look, in what is the start of a 3.5-year-mission to examine stars with known exoplanets.

The CHaracterising ExOPlanets Satellite (CHEOPS) a joint European / Swiss mission, was launched on December 18th, 2019 by a Soyuz-Fregat from Guiana Space Centre in Kourou, French Guiana, together with a number of other payloads. It forms the first of ESA’s new S-Class (Small Class) missions, capped at a maximum budget of €50 million apiece. It’s a small mission not just in terms of cost, but also in its physical size: CHEOPS measures just 1.5 metres on a side. Following launch, it entered a 700 km Sun-synchronous polar orbit.

The completed CHEOPS prior to being shipped for launch. The telescope cover is the circular gold element. Credit: ESA

Once there, initial testing of the satellite commenced. These first confirmed that communications between it and mission control were all working correctly. Once these had been thoroughly tested, the command was sent to boot-up the primary computer system so it could be run through a series of diagnostics before the primary science components were initialised. These tests also included the vehicle’s temperature control systems and the primary elements of the main telescope system – a 30 cm  optical Ritchey–Chrétien telescope.

CHEOPS launched on December 18th atop a Soyuz Feegat rocket from Guiana Space Centre in Kourou

These initial commissioning tests culminated in the opening of the telescope’s primary baffle – otherwise known as its lens cap. This was the most critical aspect of the initial commissioning – if the the baffle failed to hinge open, the telescope would be unable to observe its target stars.

Fortunately, the opening went as planned, allowing the final set of tests to commence. Over the next couple of months, these will see CHEOPS take hundreds of images of stars – some with exoplanets, some without, in order to examine the measurement accuracy of the telescope systems under different conditions, and confirm its operating envelope. At the same time, this period of testing will also allow this mission team to further integrate all aspects of ground operations. Again, if all goes according to plan, some of this first light images will be released by the CHEOPS science team, and the end of the tests will see the telescope commence its primary operations.

While thousands of exoplanets have been discovered, few of them have been accurately characterised in terms of both mass and diameter. This limits our ability to fully assess their bulk density, which is needed to provide clues to there composition and their possible formation history.So to help us gain better data, CHEOPS will accurately measure the size of known transiting exoplanets orbiting bright and nearby stars. These are planets that cause dips in the brightness of their parent stars as they pass between the star and Earth.

By targeting known systems, we know exactly where to look in the sky and when in order to capture exoplanet transits very efficiently. This makes it possible for CHEOPS to return to each star on multiple occasions around the time of transit and record numerous transits, thus increasing the precision of our measurements and enabling us to perform a first-step characterisation of small planets.

– Willy Benz, CHEOPS principal investigator

The transit method offer a “direct” means of detecting exoplanets, but it is not the only option open to us. A second method, generally referred to as the radial velocity method, or Doppler spectroscopy, can detect planets “indirectly”, by directing the doppler shifted “wobble” in a star’s motion. Around 30% of all exoplanets have been detected by this method, but it can be somewhat less informative than the transit method. This being the case, another aspect of the telescope’s mission will be looking at stars where orbiting planets have been detected via the radial velocity method in an attempt to detect the planets by the more direct transit method and again, by repeated observations, allow scientists to start to characterised them.

As a whole, CHEOPS will be particularly focused on exoplanets characterised as “super-Earths” – those thought to be between Earth and Neptune in size, many of which may well be solid in nature. While it will be able to characterise these exoplanets with a new level of precision, its work will pave the ways for follow-up observations in the future by telescopes like the James Webb Space Telescope (JWST – operating in the infra-red), and by large ground-based telescopes like the 40m Extremely Large Telescope currently under construction, allowing them to both refine the CHEOPS data and add to it.

Continue reading “Space Sunday: telescopes, lunar plans and Voyager 2”

Space Sunday: a farewell to Spitzer, capsules, stars and space planes

A composite image of NASA’s Spitzer Space Telescope. Credit: NASA

The end of January 2020 brings with it the end of a 16-year mission to explore the galaxy in the infra-red, as the Spitzer Space Telescope (SST) is shut down.

Launched in 2003, Spitzer was one of NASA’s four Great Observatories, following in the footsteps of the Hubble Space Telescope and the Chandra X-ray Observatory. Its infra-red vision has allowed Spitzer to peer through the dusty reaches of the cosmos to witness stellar nurseries, provide insight into the deaths of stars and the very formation of the universe, and increase our understanding of the structure of galaxies and the nature of black holes.

Spitzer operated as planned for 5.5 years – three years longer than its initial primary mission – until a lack of coolant prevented the telescope from operating within its planned low temperature range. A switch to a warmer operating mode allowed the telescope’s mission to be extended another 10.5 years, albeit it with only two of its sciences instruments able to function in the higher temperature range.

NASA’s four space-based Great Observatories. Credit: NASA

The official reason for ending the mission, even though the two remaining IRAC instruments remain operational, is issues of balancing operational requirements with those of power generation and communications. Spitzer occupies a similar orbit to Earth but is moving more slowly; as the gap between them widens, so to does the triangle formed by the Sun, Earth and the telescope, and it has now reached a point where in is impossible for the telescope to maintain both line-of-sight communications with Earth and keep its solar panels pointing to the Sun to generate power. Add to this the need to orient the telescope to observe study targets, and operating the telescope has become an increasingly complex and fuel-costly dance.

In 2017, NASA attempted to spin-off the telescope’s operations and management to academic institutions in 2017, but was unsuccessful. So, on January 29th, Spitzer will transmit to Earth the last of the data it has gathered, then on January 30th, it will be put into a hibernation mode, oriented in a permanent “sun-coning attitude”. In theory, it would be possible to recover the telescope from this state at some point in the future, except for the fact that the custom ground system for operating Spitzer is to be dismantled after the telescope has been shut down.

Overall, the cost of the Spitzer mission from launch to this final close-out will have been US $1.3 billion, a modest price for the wealth of data the mission has returned to Earth: over 8,700 scientific papers related to Spitzer’s discoveries and data have been published. However, the shut down will effectively bring space-based infra-red observations of the galaxy around us to an end – at least until the James Webb Space Telescope commences operations. This is expected to launch in 2021.

The telescope has made many discoveries beyond the imaginations of its designers, such as planets outside our solar system, called exoplanets, and galaxies that formed close to the beginning of the universe. We have a lot of new questions to ask about the universe because of Spitzer. It’s very gratifying to know there’s such a powerful set of capabilities coming along to follow up on what we’ve been able to start with Spitzer.

– Michael Werner, Spitzer project scientist, NASA Jet Propulsion Laboratory

China Prepares to Test Launch Its Next Generation Crew Vehicle

In 2018, I first wrote about China’s upcoming “next generation” crewed space vehicle that will eventually replace the Soyuz-derived Shenzhou craft. Since then, work has been proceeding with the design, with structural test articles being rigorously tested together with the vehicle’s parachute and landing systems, while the first flight-ready unit has also been under development and assembly.

The first of China’s next generation crew capsules being mated to its Service Module. Credit: CAST

The new craft mirrors both the the Apollo Command and and Service Module approach to crewed space systems and Boeing’s CST-100 Starliner. Like the former, it comprises a conical crew capsule supported in space be a cylindrical Service Module equipped with a single large motor and designed to provide the capsule with power and life support whilst in space. The Service Module is also thought to offer two variants: a small version for operations in Earth orbit, and a larger unit to help support missions further afield – such as to the Moon.

Like Boeing’s Starliner, the capsule is designed to carry up to 6 crew, or a combination of crew and cargo, and can be re-used up to 10 times. At the end of each flight, it will make a dry land touchdown using both parachutes and air bags.

The 14-tonne (l) and 20-tonne next generation Chinese crewed vehicles – remarkably similar to Boeing’s CST-100 Starliner. Credit: Beijing Institute of Space Mechanics and Electronics

On January 20th, the flight test vehicle arrived at China’s Wenchang Satellite Launch Centre on Hainan island in the South China Sea. It will be integrated with a Long March 5B launch vehicle – currently China’s most powerful booster – ready to for an uncrewed flight that will carry it some 8,000km from Earth before returning and making a soft landing. This first flight could take place as early as April 2020.

The vehicle has yet to be given an official name, and no date has been given for its possible entry into service. However, it is seen as a key component in China’s upcoming new space station – construction of which may also start this year – and in their human Moon exploration programme.

Continue reading “Space Sunday: a farewell to Spitzer, capsules, stars and space planes”