Space Sunday: the last goodbye, super-Earths and spaceplanes

September 14th, 2017. One of the final images captured by Cassini as it approaches Saturn for the last time, with mysterious Enceladus visible beyond the limb of the planet. The thin blue haze seen in the picture is the atmosphere above Saturn’s cloud tops, where the spacecraft finally disintegrated. Credit: NASA/JPL / Space Science Institute

At 12:55 UT (13:55 BST, 08:55 EST, 05:55 PDT) the very last signal was received from the NASA / ESA Cassini spacecraft as it entered the upper reaches of Saturn’s atmosphere before disintegrating and burning-up. It was received 83 by NASA’s ground station near Canberra, Australia, 83 minutes after being transmitted – by which time the probe had already been destroyed.

At mission control, at the Jet Propulsion Laboratory, operated jointly by NASA and Caltech in Pasadena, California, it was an emotional moment. For many, the mission had been a part of their daily lives for nigh-on 20 years.

“The signal from the spacecraft is gone and, within the next 45 seconds, so will be the spacecraft,” Cassini programme manager Earl Maize announced, his voice catching, to the team gathered in mission control. “I’m going to call this the end of mission.” He then turned to Spacecraft Operations Team manager Julie Webster and hugged her, before giving Linda Spilker, the Cassini Project Scientist a hug as well. That loss of signal came within 30 seconds of the time predicted ahead of Cassini’s final dive.

Cassini Project Manager Earl Maize (centre left) and Spacecraft Operations Team Manager Julie Webster embrace after the Cassini spacecraft plunged into Saturn, Friday, September. 15, 2017. Credit: NASA / Joel Kowsky

As I reported last week, The Cassini-Huygens mission has been an incredible voyage of discovery, revealing so much about Saturn, its rings and retinue of moons, including hints on the evolution of life itself and revealing how moons Titan and Eceladus may have all the right conditions to support basic life while Tethys could – like Enceladus – have a liquid water ocean under its ice.

Cassini’s final approach commenced on September 11th, as it started back towards Saturn having made a final pass between the planet and its rings and looping away from both the week before. Passing by Titan, and once more using the moon’s gravity to push it into the correct trajectory, the probe headed back for its final encounter with Saturn. The Titan fly-by presented a last opportunity to image and study the moon before Cassini’s imaging system was focused on Saturn for the first part of the final approach. Imaging Saturn ended on Thursday, September 14th as the vehicle re-oriented itself to gather as much data on its brief passage into the upper reaches of Saturn’s atmosphere.

Time line of the final plunge. Credit: NASA

As I’ve previously noted in my Cassini mission updates, the primary reason for sending the probe into Saturn’s atmosphere was because it had exhausted almost all of its on-board fuel supplies used to orient itself and to adjust its flight through the Saturnian system, and the mission team didn’t want to leave the probe tumbling around Saturn’s moons where it might one day impact one of them and contaminate it with both Earthly microbes which may be dormant inside the vehicle, and which radioactive debris from its electrical power generators.

However, an alternative would have been to use the last of the vehicle’s fuel to boost it away from Saturn and out into space, but the scientific return promised by a final plunge into the planet was too good to refuse. “Saturn was so compelling, so exciting, and the mission we finally came up with was so rich scientifically that we just couldn’t — we had to finish up at Saturn, not some place else.” Earl Maize stated during a press conference after the probe’s fiery end.

There are currently no planned missions that will follow Cassini-Huygens to Saturn, although there are proposals to send missions to Titan. However, while the active part of the mission has come to an end, it’s not an end of the mission’s science.

“We have collected this treasure trove of data, so we have decades of additional work ahead of us,” Linda Spilker, the Cassini Mission Scientist said. “With this fire hose of data coming back basically every day, we have only been able to skim the cream off the top of the best images and data. But imagine how many new discoveries we haven’t made yet! The search for a more complete understanding of the Saturn system continues, and we leave that legacy to those who come after, as we dream of future missions to continue the exploration we began.”

As a closing note – for now – it’s not often that a space mission gains an official music video; but Cassini-Huygen has been a major inspiration for many over the past two decades, it has earned not one, but three official music videos which form a suite of music by three composes: Iniziare (Italian: “to start” by Sleeping At Last, aka Ryan O’Neal), Kanna (Icelandic: “Explore” by Sarah Schachner) and Amaiera (“end” or “stop” by Joseph Trapanese). I’ve embedded the first part below.

SpaceX Launch X-37B

On Thursday, September 7th, a SpaceX Falcon 9 booster launched the US Air Force X-37B secret mini-shuttle into orbit ahead of the Florida coast being hit by hurricane Irma. It marked the 13th Falcon 9 launch of 2017, and the fifth flight overall for the X-37B.

The USAF’s X-37B Orbital Test Vehicle (OTV) on the runway at Kennedy Space Centre, May 7th, 2017, at the end of the 717-day OTV-4 mission, being “safed” by a Boeing team in protective suits to guard against harmful fumes and gases given off by the vehicle. Credit: USAF

OTv-5 (Orbital Test Vehicle flight 5) saw the automated spaceplane placed into a higher inclination orbit than previous missions – thus expanding the vehicle’s flight envelope. However, in keeping with previous missions, the USAF has remained mostly silent on the mission’s objectives or its intended duration, revealing only that one experiment flying is the Advanced Structurally Embedded Thermal Spreader II (ASETS-II), which will measure the performance of an oscillating heat pipe.

Previous OTV missions have been long-duration flights, with the maiden flight in 2010 lasting 224 days and 9 hours, which each mission lasting longer than the last, with the last mission completed, OTV-4,  totalling 717 days and 20 hours in orbit. The flights have, up until now, alternated between the two known X-37B vehicles, so although it has not been confirmed, it is believed this mission is being carried out by the first X-37B to fly in space.

The SpaceX Falcon 9 first stage descends to a safe landing at Cape Canaveral Air Force Station after sending the X-37B OTV on its way to orbit on September 7th, 2017. Credit: Ken Kremer

The launch took place from Kennedy Space Centre’s Launch pad 39A, which SpaceX has leased from the US space agency and refurbished to handle Falcon 9 and Falcon Heavy launches – and which is now liable to be the pad from which the company’s massive ITS super-heavy rocket will depart when it enters operations in the 2020s. After separating from the upper stage and its cargo, the Falcon 9 first stage performed a “burn-back” manoeuvre and flew back to SpaceX’s dedicated Landing Zone-1 (LZ-1) at Cape Canaveral Air Force Station alongside Kennedy Space Centre, offering spectators a superb view of the landing.

Continue reading “Space Sunday: the last goodbye, super-Earths and spaceplanes”


Space Sunday: water, spaceplanes and clockwork rovers

TRAPPIST-1 compared in size to our own Sun. Credit: NASA.

Since the February 2017 announcement on the discovery of seven rocky planets orbiting the nearby red dwarf star TRAPPIST-1, multiple studies have been conducted to ascertain whether any of the planets might harbour conditions suitable for life. The nature of their parent star would suggest this to be unlikely. However, an international team utilising the Hubble Space Telescope (HST) to study the TRAPPIST-1 system believe they’ve found evidence that some of the planets have the right conditions to allow liquid water to exist.

Vincent Bourrier, from the Observatoire de l’Université de Genève in Switzerland, and his team used the  Space Telescope Imaging Spectrograph (STIS) to study the amount of ultraviolet radiation each of the TRAPPIST-1 planets receives. If there were too much UV light, no water could survive on the surface because the water molecules would break up and escape through the top of the atmosphere as hydrogen and oxygen gas.

The team found that the inner planets in the system – TRAPPIST-1b and 1c – receive so much UV radiation from their sun, they may have lost more than 20 Earth-oceans worth of water in the course of their history, estimated to be between 5.4 and 9.8 billion years old. Thus, they are almost certainly devoid of water, and their surfaces are likely sterile. However, the findings also suggest the outer planets in the system – including the three within TRAPPIST-1’s habitable zone, may have lost less than three Earth-oceans’ worth of water throughout their history, and could possibly still possess liquid water, making them more amenable for life to rise.

As well as suggesting some of the TRAPPIST-1 planets may have liquid water present, the study has broader implications for the potential of other exoplanets harbouring life. Up to 70% of the stars in the Milky Way are believed to by M-class red dwarfs – and the majority of rocky exoplanets thus far found are orbiting such stars. So this study might indicate that many more of the exoplanets orbiting such stars could support liquid water and, perhaps, conditions suitable for life. However Bourrier and his colleagues emphasise that the study is not conclusive, and further research is needed to determine if any of the TRAPPIST-1 planets are actually watery.

SNC Prepares Dream Chaser for Glide Flight Testing and UN Mission

Sierra Nevada Corporation (SNC) carried out a “captive / carry” test of a Dreamer Chaser Cargo vehicle test article on August 31st, 2017. The flight, with the vehicle slung beneath a helicopter forms the first step towards the Dream Chaser Cargo carrying out glide flights and landings.

During the test, SNC collected data on the vehicle’s performance in flight, including operation of radar altimeters, air data probes and other systems that cannot be fully tested on the ground. The captive /  carry test followed a series of ground tests where the vehicle was towed behind a truck down a runway at speeds of up to 100 kph to ascertain its ground handling on landing.

The Dream Chaser Cargo test article is lifted aloft by helicopter in a captive/carry test. Credit: Sierra Nevada Corporation

SNC developed Dream Chaser to transport astronauts to and from the ISS. However, NASA selected capsule designs by SpaceX and Boeing. After a protest over the decision, filed with the U.S. Government Accountability Office, failed, SNC turned their attention to other potential uses for Dream Chaser.

One of these has been the development of a cargo variant to service the International Space Station (ISS) alongside existing resupply contractors,  Orbital ATK and SpaceX, and in 2016, NASA confirmed Dream Chaser Cargo has been selected to fly resupply missions to the ISS between 2019 and 2024.

On July 19th, 2017, it was announced that SNC had signed a contract with United Launch Alliance for the first two launches of these resupply missions, using the Atlas 5 552 launch vehicle. The first launch is scheduled for 2020 and the second in 2021, although NASA has yet to formally order any Dream Chaser flights.

A Dream Chaser Cargo vehicle will also be used in 2021 to launch the first United Nations mission into space. The United Nations Office of Outer Space Affairs (UNOOSA) said an agreement between them and SNC to fly the dedicated Dream Chaser mission is part of a broader effort by the office to increase access to space to emerging nations.

The mission will be open to all nations, but with a particular emphasis on those that don’t have the capabilities to fly their own experiments in space. UNOOSA are in the process of soliciting payload proposals with a goal of selecting payloads by early 2018 so that the winning countries have time to build them for a 2021 launch.

Unlike the majority of Dream Chaser Cargo missions, which will focused on ISS resupply work, the UNOOSA flight will see the vehicle placed in orbit around the Earth, and SNC have indicated the vehicle will be capable of operating freely in orbit for extended periods of time, should the UN desire a longer mission.

While billed as the UN’s first space mission, the Dream Chaser flight is part of UNOOSA’s Human Space Technology Initiative, launched in 2010 with the goal of providing developing countries the possibility to access space in microgravity conditions. Currently, the initiative includes two other major projects. The first is a cooperative project with the Japan Aerospace Exploration Agency (JAXA), designed to give developing nations the opportunity to launch cubesats from the ISS. Another programme, to be operated in cooperation with China’s space programme, will allow UN-backed missions to be flown aboard China’s space station, when it becomes operational in 2020.

Continue reading “Space Sunday: water, spaceplanes and clockwork rovers”

Space Sunday: an eclipse, a star, a moon and an asteroid

Eclipse 2017: the Moon’s umbra passes over the Earth as witnessed by the astronauts aboard the International Space Station, August 21st, 2017. Credit: NASA.

Eyes were on the sky across the world on Monday, August 21st, 2017, either directly or via live stream and television broadcasts, as people watched the 2017 total eclipse of the Sun. Millions of people in the continental United States were particularly well-placed to enjoy the spectacle first-hand as the line of totality tracked diagonally cross the country from Oregon to South Carolina.

NASA reported that some 90 million people viewed their Eclipse 2017 website on the day, with 40 million staying to watch their live stream of the event. Other organisations providing live streams of the eclipse also reported high numbers of hits / views of their coverage.

As one might expect, the event gave rise to some stunning photos and images which have been posted on Pinterest, Flickr, and other photo sharing websites, plus videos and animations. So much so that picking some out to highlight the event is  tough task – I suggest anyone wanting to recapture the event spend time on-line Googling the 2017 eclipse for reports and images. However, there were a couple of images that did leap out to me when looking through reports and photo sites.

The crew of the International Space Station (ISS), Commander Fyodor Yurchikhin and Sergey Ryazanskiy from Roscosmos, Randy Bresnik, Jack Fischer and Peggy Whitson from NASA and Paolo Nespoli from the European Space Agency), witnessed the Moon’s shadow on the Earth three times as the ISS repeatedly crossed the path of the eclipse as the space station orbits the Earth. This resulted in some remarkable images, including the one at the top of this report.

Uncredited image of an airliner passing between the eclipse and the photographer – note the solar prominence at the 1 and 3 o’clock positions. Click for full size.

One of the reasons astronomers are interested in total eclipses is that they provide ideal opportunities for studying the Sun’s corona and prominences – of which there were a number to be observed during this event. This is reflected in the second of my choices (above), which shows two prominences at the one and three o’clock positions rising “above” the Moon’s disk, as an airliner passes through the shot as well.

Jeff Seibert posted a video of images he captured of the eclipse from Santee, South Carolina. These offer a time-lapse of the start of the eclipse, views the famous “diamond ring” which immediately precedes / follows the period of totality and totality itself, revealing the Sun’s corona.

Five eclipses will take place in 2018. Two of these are total lunar eclipses and three are partial solar eclipses:

  • January 31st, 2018: total lunar eclipse, visible from north / east Africa, Antarctica, Asia, Australia, north / east Europe,  India, North America, north / west South America.
  • February 15th, 2018: partial solar eclipse, visible from Antarctica and southern South America.
  • July 13th, 2018: partial solar eclipse, visible from southern Australia
  • July 27th/28th total lunar eclipse: Africa, Antarctica, much of Asia, Australia, much of Europe, southern part of North America, South America.
  • August 11th, 2018: partial solar eclipse, visible from Arctic, north / west Asia, north / east Europe, northern North America.

The next two total solar eclipses will occur on July 2nd, 2019 and December 14th, 2020. he line of totality for both runs across South America.

Tabby’s Star: Giant Ringed Planet to Blame?

I’ve written several times over the last year about the mystery of Tabby’s Star – more formally known KIC 8462852, an F-type main-sequence star located in the constellation Cygnus approximately 1,480 light years from Earth. It’s been of particular interest to astronomers because it experiences massive and irregular dips in brightness of up to 22% at a time, which last for several days before it reverts to its “normal” brightness once more.

Numerous theories have been put forward on why the star is acting so oddly, from the idea that a race of aliens are building a mega-structure – perhaps a Dyson Sphere around it, through to it being a cloud of comets orbiting the star at a great distance, or that it is some kind of “avalanche” type of activity within the star itself.

In April / May, 2017, KIC 8462852 started on a further cycle of dimming, leading to a world-wide bulletin for astronomers to observe it. This resulted in a further theory that the cause of the dimming might be a combination of two clouds of asteroids and a giant ringed planet orbiting the star.

An artist’s impression of exoplanet J1047, thought to have an extended ring system around it. Could a similar planet and ring system account for the fluctuations we see in Tabby’s Star’s brightness? Credit: Ron Miller

This last theory relied on the asteroids occupying the trojan positions either side of the planet as all three orbit the star, making it a complex model. However, another team of researchers from the University of Antioquia in Colombia have now also suggested a ringed planet might be responsible, but in a way which doesn’t require the existence of massive asteroid clouds sharing in the planet’s orbit.

The researchers used data from past dimming events at KIC 8462852 to build a model of the system which shows that a Jupiter / Saturn sized gas giant, orbiting the star at a distance of about 0.1 AU and with an extended Saturn-style system of rings tipped at an angle relative to the planet’s orbital plane around the star could account for KIC 8462852’s apparent fluctuations in brightness.

At such a distance from the parent star, an inclined ring system would not remain relatively constant if form and position, as is the case with Saturn’s rings. Instead, it would undergo short-term changes in shape and orientation as a result of KIC 8462852’s gravitational influence. The researcher’s model shows that these changes would likely lead to changes of the depth of opacity in the ring system, further contributing to the witnessed irregularities in the star’s apparent brightness. As the rings and planet periodically transit between the star and observers on Earth.

A further compelling aspect of this research is that the oscillations in the proposed ring system of any planet orbiting Tabby’s Star could also explain the strangeness witnessed in the  light-curves found in a number of other stars believed to have planets orbiting them. In other words, it is entirely possible astronomers have already observed similar planetary ring systems elsewhere in the galaxy, but simply haven’t been recognised as such.

Like the other theories for KIC 8462852’s behaviour, this latest idea is not definitive; further, better studies of the star – potentially by the James Webb Space Telescope – are required before anything might be known with certainty. However, of all the proposals put forward thus far for the star’s odd behaviour when observed from our solar system, this one does have the virtue of being perhaps the simplest and the first to offer incidental corroboration through the behaviour seen when some other stars believed to have planets orbiting them.

Continue reading “Space Sunday: an eclipse, a star, a moon and an asteroid”

Space Sunday: total eclipse and exoplanet update

2016 total eclipse Credit: NASA Exploratorium webcast

On Monday, August 21st, the continental United States will experience its first total eclipse of the sun for 38 years (the last total eclipse visible from the USA having occurred in 1979). Providing the weather holds good along the path of the eclipse, an estimated 220 million people will be able to see the event – providing they take the proper precautions.

An eclipse is a periodic event, occurring when the Moon passes between the Sun and Earth and either fully or partially occults (blocks) the Sun’s light. This can happen only at new moon, when the Sun and the Moon are in conjunction as seen from Earth, in an alignment referred to as syzygy. There are actually four types of eclipse:

  • Partial – this occurs when the Sun and Moon are not exactly in line with the Earth, and so the Moon only partially obscures the Sun. Partial eclipses are virtually unnoticeable in terms of the sun’s brightness, as it takes well over 90% coverage to notice any darkening at all.
  • Annular – occurs when the Sun and Moon are exactly in line with the Earth, but because of the variations in the Earth’s distance from the Sun, and the variations in the Moon’s distance from the Earth, the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus, surrounding the dark disk of the Moon.
  • Total – occurs when the dark silhouette of the Moon completely obscures the intensely bright light of the Sun, allowing the much fainter solar corona to be visible. The complete coverage of the Sun’s disk by that of the moon – referred to as totality – occurs at its best only in a narrow track on the surface of Earth.
  • Hybrid (also called annular/total eclipse) – this shifts between a total and annular eclipse. At certain points on the surface of Earth, it appears as a total eclipse, whereas at other points it appears as annular. Hybrid eclipses are comparatively rare.

The last total eclipse took place in March 2016, and was visible from South/East Asia, North/West Australia, the Pacific and Indian oceans. The 2017 event will be visible in partial forms across every continent except Antarctica and Australia. However, the path of totality will only be visible across the continental United States.

Although totality slices through the U.S., partial phases of the eclipse touch on every continent except Antarctica and Australia. Credit: Michael Zeiler / The Great American Eclipse – click for full size

The path of totality will run from Oregon to South Carolina, as will be around 113 kilometres (70 miles) wide, offering people along it an unrivalled opportunity to view the eclipse  – weather permitting -, providing the right precautions are taken.

The most important aspect of viewing an eclipse “live” is never look directly at the Sun, even during the period of totality; you should at least use a solar filter or viewer. However, if you don’t have one or the other or any specialised kit, the best way to see the eclipse in the flesh is via pinhole projection. For those who are unable to see the eclipse first-hand, there are a wide variety of ways to watch the event on television or the Internet, including:

  • NASA Total Eclipse live stream is providing options to watch through NASA Edge, NASA TV, Ustream, YouTube and more. NASA’s Facebook page. These will show images of the eclipse, from 11 spacecraft, three aircraft and from more than 50 high-altitude balloons, and the astronauts on the International Space Station.
  • Slooh, the on-line community observatory, will run a webcast starting at 12:oo noon EDT (1600 GMT), as a part of a 3-day celebration of the eclipse.
  • The Virtual Telescope Project is hosting a free online observing session with views of the total solar eclipse beginning at 13:00 EDT (17:00 GMT).
  • The Eclipse Ballooning Project will be broadcasting live views of the eclipse from the edge of space via more than 57 cameras sent up on weather balloons.
  • CNN and Volvo will be providing a 360-degree view of the eclipse with 4K resolution from different locations along the eclipse path. The stream will also be viewable in virtual reality, which people can navigate by moving a phone or virtual reality headset. The live stream begins at 12:03 p.m. EDT (16:03 GMT).
  • ABC will air a two-hour special on the eclipse starting at 13:00 EDT (17:00 GMT). The broadcast will also be available on Facebook Live and YouTube

There are a number of terms common to eclipses which are worth mentioning for those who wish to follow the event, but are unfamiliar with the terminology. These include:

Eclipse Types (Moon and Sun not to scale). Credit: Cmglee
  • The umbra, within which the object in this case, the Moon) completely covers the light source (in this case, the Sun’s photosphere).
  • The antumbra, extending beyond the tip of the umbra, within which the object is completely in front of the light source but too small to completely cover it.
  • The penumbra, within which the object is only partially in front of the light source.
  • Photosphere, the shiny layer of gas you see when you look at the sun.
  • Chromosphere, a reddish gaseous layer immediately above the photosphere of the sun that will peak out during the eclipse.
  • Corona, the light streams that surround the sun.
  • First contact, the time when an eclipse starts.
  • Second contact, the time when the total eclipse starts.
  • Third contact, the time when the total eclipse ends.
  • Fourth contact, the time at which the eclipse ends.
  • Bailey’s beads, the shimmering of bright specks seen immediately before the moon is about to block the sun.
  • Diamond ring, the last bit of sunlight you see right before totality. It looks like one bright spot (the diamond) and the corona (the ring).

A total eclipse occurs when the observer is within the umbra (they are standing in the shadow cast by the Moon); an annular eclipse when the observer is within the antumbra, and a partial eclipse when the observer is within the penumbra.

As well as the passage of the Moon between the Earth and Sun, there are a number of Earthly effects to look for if you are in the path of totality, such as a the 360-degree sunset. This may also be accompanied by an “eclipse wind” as temperatures suddenly drop. And, of course, there is the rousing of nocturnal animals, fooled by the darkness, followed by a false dawn as the Moon moves away from between the Earth and the Sun, and an accompanying dawn chorus.

The period of totality lasts only a few minutes but offers a superb opportunity for observing the Sun and its corona – hence why NASA is using a chain of three aircraft to “chase” the eclipse as the Moon’s shadows travels at an average speed of 3,683 km/h (2,288 mph) west-to-east, enabling them to carry out an extended study of the corona.

The Moon’s shadow on Earth, as seen from the International Space Station on March 29th, 2006 as it passes over southern Turkey, Northern Cyprus and the Mediterranean Sea. Credit: NASA

As a point of historical interest, August 21st marks the 103rd anniversary of the 1914 total eclipse, which was seen from Scandinavia through to Turkey, the middle east and India. It was the subject of a number of expeditions being sent eastwards to the Baltic and Ukraine by Britain and other European nations with the intention of studying it – only for the conflagration of the First World War to erupt.

The war foiled attempts by a British expedition which intended to use the eclipse as a means to measure relativity; however, it did give rise to another mystery: whether or not a film of the eclipse apparently made in Sweden in 1914 is the real deal or not. If it is, it might be the oldest surviving footage of an eclipse.

If you are on the path of totality, and plan to view the eclipse, do please take the proper precautions and I hope the weather cooperates with you. I’ll be following things on-line.

Continue reading “Space Sunday: total eclipse and exoplanet update”