Category: Space Sunday

Space Sunday: Voyager at 40

Posted on by Inara Pey
Voyager: 40 years on. Credit: NASA

August 20th 2017 marks the 40th anniversary of the launch of Voyager 2, which with its sister craft Voyager 1 (launched on September 5th, 1977) are humanity’s furthest-flown operational space vehicles, with Voyager 1 being the most distant human made object from Earth, at some 140 AU (AU= astronomical unit, the average distance between the Earth and the Sun; 140 AU equates to about 20.9 billion kilometres / 13 billion miles).

Despite being so far away from Earth, both craft are still sending data back to Earth as they fly through the interstellar medium in the far reaches of the solar system (the Pioneer 10 and Pioneer 11 craft which pre-date the Voyager programme by some 5 years, ceased transmissions to Earth in January 2003 and September 1995 respectively, although Pioneer 10 is the second most distant human made object from Earth after Voyager 1).

The Voyager programme stands as one of the most remarkable missions of early space exploration. Originally, the two vehicles were to be part of NASA’s Mariner programme, and were at first designated Mariner 11 and Mariner 12 respectively. The initial Mariner missions – 1 through 10 – were focused on studying the interplanetary medium and  Mars, Venus and Mercury (Mariner 10 being the first space vehicle to fly by two planets beyond Earth – Venus and Mercury – in 1974). Mariner 11 and Mariner 12 would have been an expansion of the programme, intended to perform flybys of Jupiter and Saturn.

A drawing of the Voyager vehicles. Credit: NASA/JPL (click for full size)

However, in the late 1960s Gary Flandro, an aerospace engineer at the Jet Propulsion Laboratory (JPL) in California noted that in the late 1970s, the outer planets would be entering a period of orbital alignment which occurs once every 175 years and which could be used to throw a series of probes out from Earth, which could then use the gravities of the worlds they encountered to “slingshot” them on to other targets. This led to the idea of a “Grand Tour” mission: sending pairs of probes which could use these gravity assists to fly by Jupiter, Saturn, Uranus, Neptune and Pluto in various combinations.

Funding limitations eventually brought an end to the “Grand Tour” idea, but the planetary alignment was too good an opportunity to miss, and so elements of the idea were folded into the Voyager Programme, which would utilise Mariner 11 and Mariner 12. However, as the mission scope required some significant changes to the vehicles from the basic Mariner design, they were re-designated as Voyager class craft.

(As an aside, the Mariner class is the longest-lived of NASA’s space probe designs; as well as the ten missions of the 1960s and 1970s which carried the design’s name,  the Mariner baseline vehicle – somewhat enlarged – was used for the Viking 1 and Viking 2 orbiter missions to Mars, and formed the basis of the Magellan probe (1989-1994)  to Venus and the Galileo vehicle (1989-2003) which explored Jupiter. And uprated and updated baseline Mariner vehicle, designated “Mariner Mark II”, formed the basis of the Cassini vehicle, now in the terminal phase of its 13-year study of Saturn and its moons.)

Each of the Voyager mission vehicles is powered by  three plutonium-238 MHW-RTG radioisotope thermoelectric generators (RTGs), which provided approximately 470 W at 30 volts DC when the spacecraft was launched. By 2011, both the decay of the plutonium and associated degradation of the thermocouples that convert heat into electricity has reduced this power output by some 57%, and is continuing at a rate of about 4 watts per year.

To compensate for the loss, various instruments on each of the vehicles have had to be turned off over the years. Voyager 2’s scan platform and the six instruments it supports, including the vehicle’s two camera systems, was powered-down in 1998. While the platform on Voyager 1 remains operational, all but one of the instruments it supports – the ultraviolet spectrometer (UVS) – have also been powered down. In addition, gyro operations ended in 2016 for Voyager 2 and will end in 2017 for Voyager 1. These allow(ed) the craft to rotate through 360 degrees six times per year to measure their own magnetic field, which could then be subtracted from the magnetometer science data to gain  accurate data on the magnetic fields of the space each vehicle is passing through.

However, despite the loss of capabilities, both Voyager 1 and Voyager 2 retain enough power to operate the instruments required for the current phase of their mission – measuring the interstellar medium and reporting findings back to Earth. This phase of the mission, officially called the Voyager Interstellar Mission, essentially commenced in 1989 as Voyager 2 completed its flyby of Neptune, when the missions as a whole was already into their 12th year.

A plume rises 160 km (100 mi) above Loki Patera, the largest volcanic depression on Io, captured in March 1979 by Voyager 1. Credit: NASA/JPL

Voyager 2 was launched on August 20th, 1977. Of the two vehicles, it was tasked with the longer of the planned interplanetary missions, with the aim of flying by Jupiter, Saturn, Uranus and Neptune. However, the latter two were seen as “optional”, and dependent upon the success of Voyager 1.

This was because scientists wanted the opportunity to look at Saturn’s moon Titan. But doing so would mean the Voyager craft doing so would have to fly a trajectory which would leave it unable to use Saturn’s gravity to swing it on towards an encounter with Uranus. Instead, it would head directly towards interstellar space.

So it was decided that Voyager 1, which although launched after Voyager 2 would be able to travel faster, would attempt the Titan flyby. If it failed for any reason, Voyager 2 could be re-tasked to perform the fly-past, although that would also mean no encounters with Uranus or Neptune. In the end, Voyager 1 was successful, and Voyager 2 was free to complete its surveys of all four gas giants.

Along the way, both missions revolutionised our understanding of the gas giant planets and revealed much that hadn’t been expected, such as discovering the first active volcanoes beyond Earth, with nine eruptions imaged on Io as the vehicles swept past Jupiter. The Voyager missions were also the first to find evidence that Jupiter’s moon Europa might harbour a subsurface liquid water ocean and to return the first images of Jupiter’s tenuous and almost invisible ring system. Voyager 1 was responsible for the first detailed examination of Titan’s dense, nitrogen-rich atmosphere, and Voyager 2 for the discovery of giant ice geysers erupting on Neptune’s largest moon, Triton. In addition, both of the Voyager vehicles added to our catalogues of moons in orbit around Jupiter and Saturn, and probed the mysteries of both planet’s atmospheres, whilst Voyager 2 presented us with our first images of mysterious Uranus and Neptune – and thus far remains the only vehicle from Earth to have visited these two worlds.

This is the last full planet image captured of Neptune. Taken by Voyager 2 on August 21st, 1989, from a distance of 7 million km (4.4. million mi). A true colour image white balanced to reveal the planet under typical Earth lighting conditions, it shows Neptune’s “Great Dark Spot” and surrounding streaks of lighter coloured clouds, all of which persisted through the period of Voyager 2’s flyby. More recent Hubble Space Telescope images suggest the “Great Dark Spot”, initially thought to be a possible cloud / storm formation, similar to Jupiter’s Great Red Spot, has vanished, leading to speculation that it may have actually been a “hole” in a  layer of Neptune’s layered clouds. Credit: NASA/JPL

The flyby of Neptune also sealed Voyager 2’s future. Scientists were keen to use the flyby of the planet to take a look at Triton, Neptune’s largest moon. However, because Triton’s orbit around Neptune is tilted significantly with respect to the plane of the ecliptic, Voyager 2’s course to Neptune  had to be adjusted by way of a gravitational assist from Uranus and a number of mid-course corrections both before and after that encounter, so that on Reaching Neptune, it would pass over the north pole, allowing it to bent “bent” down onto an intercept with Triton while the Moon was at  apoapsis – the point furthest from Neptune in its orbit – and well below the plane of the ecliptic. As a result, Voyager 2 passed over Triton’s north pole 24 hours after its closest approach to Neptune, its course now pointing it towards “southern” edge of the solar system.

Continue reading “Space Sunday: Voyager at 40” →

Space Sunday: Curiosity’s 5th, Proxima b and WASP-121b

Posted on by Inara Pey

On August 6th 2016, NASA delivered the Mars Science Laboratory (MSL) to the surface of Mars in what was called the “seven minutes of terror” – the period when the mission slammed into the tenuous Martian atmosphere to begin deceleration and a descent to the surface of the planet which culminated in the Curiosity rover being winched down gently from a hovering “sky crane” and then lowered until its wheels made firm contact with the ground.

The “seven minutes of terror” actually had a double meaning. Not only did it represent the time MSL would smash into Mars’ atmosphere and attempt its seemingly crazy landing, at the time of the event, the distance between Earth and Mars meant it took seven minutes to be returned to mission control from the red planet. Thus, even as the initial telemetry indicating the craft was entering the upper reaches of Mars’ tenuous atmosphere was being received, mission controls knew that in reality, the landing had either succeeded or failed.

Obviously, the attempt succeeded. Everything worked flawlessly, and Curiosity was delivered to the surface of Mars at 05:17 GMT on August 6th, 2012 (01:17, August 6th EDT, 22:17 PDT, August 5th). In the five years since that time, it is helped revolutionise our understanding of that enigmatic world – as well as adding somewhat to its mystery.

To call the mission a success is not an exaggeration; within weeks of its arrival inside the 154 kilometre (96 mile) wide Gale Crater, Curiosity was examining an ancient riverbed en route to a region of the crater dubbed “Yellowknife Bay”. It was there the rover made its first bombshell discovery: analysis of the area showed that billions of years ago it was home for the ideal conditions to potentially kick-start microbial life. It was, in essence, the achievement of mission’s primary goal: to identify if Mars may have once harboured the kind of conditions which might have given rise to life.

This 360-degree view was acquired on August 6th, 2016, by Curiosity’s Mastcam as the rover neared the “Murray Buttes” on lower “Mount Sharp”. The dark, flat-topped mesa seen to the left of the rover’s arm is about 15 metres (50 ft) high and about 61.5 metres (200 ft) long. Credit: NASA/JPL / MSSS

For the first year following its arrival on Mars, Curiosity continued to survey the regions relatively close to its landing zone, finding more evidence of a benign ancient environment. Then it started out on the next phase of its mission: the long traverse towards the massive bulk of “Mount Sharp” – officially called Aeolis Mons. A huge mound of rock deposited against the crater’s central impact peak, “Mount Sharp” rises from the crater floor to an altitude of some 5.5 km (3 mi), and imagining from orbit strongly suggested its formation was due, at least in part, to the presence of water in the crater at some point in Mars’ past.

The 8 km (5 mi) trip took the rover a year to complete, in part due to its relatively slow speed, in part due to the fact is had to travel a good way along the base of “Mount Sharp” to reach a point where it could commence an ascent up the slope; but mostly because there were a number of points of interest along the way where the mission scientists  wanted to have a look around, investigate and sample.

Mount Sharp as seen from Curiosity, on January 24th, 2017. The light grey banding befpre the sandy coloured slopes is the clay unit the rover will reach in about 2 years. In front of it is the “Vera Rubin Ridge”, the next location for study by the rover. Credit: NASA/JPL / MSSS

For the last three years, the rover has been slowly making its way up “Mount Sharp”, climbing around 180 metres (600ft) vertically above the surrounding crater floor and visiting numerous points of interest – such as “Pahrump Hills”, the mixed terrain where “Mount Sharp” merges with the crater floor. Along the way, Curiosity has both confirmed that “Mount Sharp” was most likely the result of sedimentary deposits laid down during several periods of flooding in the crater before the water finally receded and wind action took over, sculpting the mound into its present shape down through the millennia.

The lakes within Gale crater may have actually been relatively short-lived, perhaps lasting just 1,000 years at a time, but Curiosity has shown that even during the dry inter-lake periods, water was very much a feature of Gale Crater, finding evidence of compressed water channels within the layers of rock which sit naturally exposed on “Mount Sharp’s” flanks.

In December 2014, NASA issued a report on how “Mount Sharp” was likely formed. On the left, the repeated depositing of alluvial and wind-blown matter (light brown) around a series of central lakes which formed in Gale Crater, where material was deposited by water and more heavily compressed due the weight of successive lakes (dark brown). On the right, once the water had fully receded / vanished from the crater, wind action took hold, eroding the original alluvial / windblown deposits around the “dry” perimeter of the crater more rapidly than the densely compacted mudstone layers of the successive lake beds, thus forming “Mount Sharp”

Alongside the sedimentary layering of the mudstone comprising “Mount Sharp” and the compressed and long-dry water channels, a further sign that the region was once water rich comes in the form of the mineral hematite, which Curiosity has found on numerous occasions. Right now, the rover is making its way towards a feature dubbed “Vera Rubin Ridge” which orbital analysis shows to be rich in this iron-bearing mineral which requires liquid water to form. Beyond that is a clay-rich unit separating the hematite rich ridge from an area which show strong evidence for sulphates. These are also indicative of water having once been present, albeit less abundantly than along “Vera Rubin Ridge”, and thus hinting at a change in the local environment. Currently, Curiosity is expected to reach this area in about two years’ time, after studying “Vera Rubin Ridge” and the clay unit along the way.

Selfies from Mars: how Curiosity has weathered the dust on Mars over five years – the dates are given as Sols – Martian days, top left and the locations where the pictures were taken. Credit: NASA/JPL

Throughout the last five years, Curiosity has remained relatively healthy. There has been the odd unexpected glitch with the on-board computers, all of which have been successfully overcome. There has been some damage to the rover’s aluminium wheels. This did give rise to concern at the time it was noted, resulting in a traverse across rough terrain being abandoned in favour of a more circuitous and less demanding route up onto “Mount Sharp”. But overall, the wheels remain in reasonably sound condition.

The one major cause for concern at present lies with Curiosity’s drill mechanism. Trouble with this first began when vibrations from the drill percussive mechanism was noted to be having a negative impact on the rover’s robot arm.

More recently – since December 2016, in fact – all use of the drill has ceased, limiting Curiosity’s sample gathering capabilities. This has been due to an issue with the drill feed motor, which extends the drill head away from the robot arm during normal drilling operations, preventing the arm physically coming into contact with targets. Attempt to rectify the problem have so far been unsuccessful, so engineers are loot at ways to manoeuvre the rover’s arm and place the drill bit in contact with sample targets, avoiding the need to use the feed motor.

So with five years on Mars under its belt, and barring no major unforeseen incidents, Curiosity will continue its mission through the next five years, further enhancing our knowledge of Mars.

Continue reading “Space Sunday: Curiosity’s 5th, Proxima b and WASP-121b” →

Space Sunday: ninja space stations, Falcons, Dragons and ET

Posted on by Inara Pey
The cislunar Deep Space Gateway with an Orion Multi-Purpose Crew Module approaching it. Credit: NASA

Lockheed Martin has announced it will build a full-scale prototype of NASA’s proposed Deep Space Gateway (DSG), a space habitat occupying cislunar space. The facility, which if built, will be both autonomous and crew-tended, and is intended to be used as a staging point for the proposed Deep Space Transport NASA is considering for missions to Mars, as well as for robotic and crewed lunar surface missions.

DSG is part of a public-private partnership involving NASA in developing technologies for carrying humans beyond low Earth orbit called Next Space Technologies for Exploration Partnerships (NextSTEP). A Phase I study for the facility has already been completed, and the full-scale prototype will be constructed as a part of the Phase II NextSTEP habitat programme, which will examine the practical issues of living and working on a facility removed from the relative proximity of low Earth orbit, outside of the relative protection of the Earth’s magnetic field and subject to delays of up to 3 seconds in two-way communications.

“It is easy to take things for granted when you are living at home, but the recently selected astronauts will face unique challenges,” said Bill Pratt, Lockheed Martin NextSTEP program manager.

“Something as simple as calling your family is completely different when you are outside of low Earth orbit. While building this habitat, we have to operate in a different mindset that’s more akin to long trips to Mars to ensure we keep them safe, healthy and productive.”

The proposed Gateway, which if built would likely enter service in 2027/2028, will be designed to make full use of the Orion Multi-Purpose Crew Module as its command and control centre, and will also use avionics and control systems designed for the likes of NASA’s MAVEN mission in order around Mars and the Juno mission at Jupiter, which will allow the facility to operate in an uncrewed automated flight mode around the Moon for up to seven months at a time.

NASA’s MPLM mission logo. Credit: NASA / Marshall Space Flight Centre

The core of the prototype will be the Donatello Multi-Purpose Logistics Module (MPLM), originally designed and built for flights aboard the space shuttle and capable of delivering up to nine metric tonnes of supplies to the International Space Station (ISS). Two of these units, Leonardo and Raffaello flew a total of 12 missions to the ISS between 2001 and 2011, with Leonardo becoming a permanent addition to the space station in early 2011. And if film and comic fans are wondering, yes, the modules were all named after a certain band of mutant ninja turtles – hence the MPLM mission logo (right).

Donatello was a more capable module than its two siblings, as it was designed to carry payloads that required continuous power from construction through to installation on the ISS. However, it was never actually flown in space, and some of its parts were cannibalised to convert Leonardo into a permanent extension to the space station. In its new role, Donatello will form the core habitat space for the DSG prototype, and will be used as a testbed for developing the living and working space in the station, which will also have its own power module and multi-purpose docking adapter / airlock unit.

The Phase II development of the DSG is expected to occur over 18 months. Mixed Reality (augmented reality and virtual reality) will be used throughout the prototyping process to reduced wastage, shorten the development time frame and allow for rapid prototyping of actual interior designs and systems. The results of the work and its associated studies will be provided to NASA to help further the understanding of the systems, standards and common interfaces needed to make living in deep space possible.

The DSG is one of two concepts NASA is considering in it attempts to send humans to Mars. The second is the so-called Deep Space Transport (DSH). This is intended to be a large vehicle using a combination of electric and chemical propulsion to carry a crew of six to Mars. It would be assembled at the Deep Space Gateway.

While having a facility in lunar orbit does make sense for supporting operations on the Moon’s surface, when it comes to human missions to Mars, the use of the DSG as an assembly  / staging post for the DST actually makes very little practical sense. Exactly the same results could be achieved from low Earth orbit and without all the added complications of lunar orbit rendezvous. The latter simply adds an unnecessary layer of complexity to Mars missions whilst providing almost no practical (or cost) benefits, and perhaps again demonstrates NASA’s inability to separate the Moon and Mars as separate destinations – something which has hindered their plans in the past.

Musk Walks Back SpaceX Aspirations

SpaceX CEO and chief designer, Elon Musk has walked back on expectations for the initial lunch of the Falcon Heavy booster and on longer-terms aspirations for the Dragon 2 crew capsule.

Musk: a successful maiden flight of the Falcon Heavy “unlikely”. Credit: Associated Press

Speaking at the International Space Station Research and Development Conference held in Washington DC in mid-July 2017, Musk indicated that a successful maiden flight of the Falcon Heavy rocket is extremely unlikely. He also indicated that the company is abandoning plans to develop propulsive landing techniques for the Dragon 2 when returning crews to Earth from the ISS – and to achieve a soft landing on Mars.

Falcon Heavy is slated to be the world’s most powerful rocket currently in operation when it enters service in 2018, capable of lifting a massive 54 tonnes to low Earth orbit – or boosting around 14 tonnes on its way to Mars. Designed to be reusable, the rocket uses three core stages of the veritable Falcon 9 rocket – one as the centre stage, two as “strap on boosters” either side of it.

But computer modelling has revealed that firing all 27 motors on the stages (nine engines apiece) at launch has dramatically increased vibrations throughout the vehicle stack, making it impossible to gauge by simulation whether or not the rocket will shake itself apart without actually flying it. Hence Musk’s statement that the maiden flight of the Falcon Heavy  – slated for later in 2017 – is unlikely to achieve a successful orbit. However, telemetry gathered during the flight – should the worse happen – will help the company more readily identify stresses and issues created by any excessive vibration, allowing them to be properly countered in future launches.

Once Falcon Heavy is fully operational, all three of the core stages are intended to return to Earth and achieve a soft landing just as they do when used as the first stage of a Falcon 9 launch vehicle, and SpaceX is also working to make the upper stage of the Falcon 9 / Falcon Heavy  recoverable as well.

Also at the conference, Musk announced SpaceX will no longer be using propulsive landings for the crewed version of their Dragon 2 space capsule, due to enter operations in 2019 ferrying crews two and from the ISS, operating alongside Boeing’s CST-100 Starliner capsule. Initial flights of the Dragon 2 were intended to see the vehicle make a “traditional” parachute descent through Earth’s atmosphere followed by an ocean splashdown – the technique currently used by the uncrewed Dragon I ISS resupply vehicle.

However, SpaceX had planned to shift Dragon 2 landings from the sea to land – using parachutes for the majority of the descent back through the atmosphere, before cutting the vehicle free and using the built-in Super Draco engines (otherwise used as the crew escape system to blast the capsule free of a Falcon launch vehicle if the latter suffers any form of pre- or post-launch failure). The engines would fire during the last few metres of decent, placing the capsule into a hover before setting it down on four landing legs.

Extensively tested in tethered “hover” flights, propulsive landings would in theory made the recovery and refurbishment of Dragon capsules for future launches a lot easier, lowering the overall operating costs for the capsule. In announcing the decision to scrap the propulsive landing approach, Musk indicated it would have unnecessarily further drawn out the vehicle’s development as SpaceX sought to satisfy NASA’s requirements for crewed vehicle operations.

The decision also affects Musk’s hope of placing a robotic mission on the surface of Mars in 2020. Under that mission, a special cargo version of Dragon 2 – called Red Dragon- would fly a NASA science payload to Mars and use supersonic propulsive landing to slow itself through the tenuous Martian atmosphere and achieve a successful soft landing. This approach was seen as ideal, because using parachutes on Mars is extremely difficult with heavy payloads – NASAs studies suggest parachute on Mars have an upper limit of payloads around 1.5-2 tonnes. A Red Dragon capsule is liable to mass around 8-10 tonnes.

SpaceX have dropped plans to use propulsive landings on both their crewed Dragon 2 vehicles returning from the ISS and on their Red Dragon automated Mars lander (above). Credit: SpaceX

However, Musk no longer believes the use of a propulsive landing mechanism is “optimal” for Red Dragon, and the company has a better way of realising their goal – although he declined to indicate what this might be. Instead, propulsive landing systems would seem to be something the company will return to in the future – particularly given their hopes of placing vehicles massing as much as 100 tonnes on the surface of Mars.

No, ET Isn’t Calling Us

The Internet was agog recently after it was announced some very “peculiar signals” had been noticed coming from Ross 128, a red dwarf star just 11 light-years away. While not known to have any planets in orbit around it, and despite the best attempts of astronomers – including the team picking up the signals at the Arecibo radio telescope, Puerto Rico – news of the signals led to widespread speculation that “alien signals” had been picked up.

The usual signals – officially dubbed the “Weird!” signal, due to the comment made in highlighting the signals in an image – were first picked up on May 12th/13th, 2017. However, it was not until two weeks later that the signals were identified and analysed, the PHL team concluding that they were not “local” radio frequency interference, but were in fact odd signals coming from the direction of Ross 128 – sparking the claims of alien signals, even though the director at PHL and the survey team leader -Abel Mendez – was one of the first to pour water on the heat of the speculation. “In case you are wondering, he stated in response to the rumours, “the recurrent aliens hypothesis is at the bottom of many other better explanations.”

The Weird! signal. Credit: UPR Aricebo

Without drawing any conclusions on what might be behind the signals, PHL liaised with  astronomers from the Search for Extra-Terrestrial Intelligence (SETI) Institute to conduct a follow-up study of the star. This was performed on Sunday, July 16th, using SETI’s Allen Telescope Array and the National Radio Astronomy Observatory‘s (NRAO) Green Bank Telescope. The fact that SETI was involved probably also helped fan the flames of “alien signal” theories. However, initial analysis of the signal and the portion of the sky where it was observed have suggested a far more mundane explanation:  geostationary satellites.

“The best explanation is that the signals are transmissions from one or more geostationary satellites,”  Mendez stated in an announcement issued on July 21st. “This explains why the signals were within the satellite’s frequencies and only appeared and persisted in Ross 128; the star is close to the celestial equator, where many geostationary satellites are placed.”

While certain this explanation is correct, Mendez does note it doesn’t account for the strong dispersion-like features of the signals (diagonal lines in the figure). His theory for this is that it is possible multiple reflections caused the distortions, but the astronomers will need more time to evaluate this idea and other possibilities.

So sorry, no ETs calling out into the night – yet.

Space Sunday: anniversaries, storms and hidden worlds

Posted on by Inara Pey
July 16th, 1969. A Saturn V rocket lifted the crew of Apollo 11 – Neil A. Armstrong, Edwin Eugene “Buzz” Aldrin Jr and Michael Collins –  on their way to the Moon, and the first manned landing there. Credit: NASA

July is a celebratory month for the US space programme. I’ve already written about July 4th marking the 20th anniversary of America – and the world – having had a continuous robotic presence on or around Mars for 20 years. This week, July 16th and July 20th mark the anniversaries of perhaps the two most momentous days in human space flight – the Lift-off of the Apollo 11 mission to land men on the lunar surface and, on July 20th, the actual landing of the Lunar Excursion Module Eagle on the Sea of Tranquillity. Neil A. Armstrong and Edwin “Buzz” Aldrin  spent 21.5 hours there, while their colleague Michael Collins (the “forgotten third man” of Apollo 11) orbited the Moon aboard the Command and Service Module Columbia, carrying out a range of science work as he awaited his compatriots’ ascent back to orbit.

The Apollo programme, although ultimately dedicated to meeting John F. Kennedy’s 1961 goal of “putting a man on the Moon and returning him safely to the Earth”, actually had its roots in President Dwight D. Eisenhower’s administration, when it was seen as a logical progression from America’s single-seat Mercury programme to a vehicle capable of carrying a crew of three on a range of mission types, including ferrying crews to a space station, performing circumlunar flights, and eventually forming part of manned lunar landings.

Apollo was a bold venture, particularly when you consider Kennedy’s directive that America commit itself to achieving a manned landing on the Moon before the end of the 1960s, given in a stirring address before Congress on May 25, 1961 came just twenty days after NASA had finally managed to pump a man  – Alan Shephard – into space on a sub-orbital flight, while their first orbital success with John Glenn was still nine months in the future. It was a programme which was politically motivated to be sure, but which nevertheless yielded scientific and technological results which helped shape both our understanding of the solar system and helped improve ours lives on many levels. It raised the potential of human space exploration high in the public consciousness, and was illuminated by tremendous successes whilst also and shadowed by moments of tragedy and near-tragedy.

A sketch of the Apollo lunar landing mission profile produced as a part of NASA’s post Apollo 8 mission report of February 1969 annotating how the mission would be undertaken

As well as the missions themselves and the hardware required to carry them out – the Command and Service Module, the Lunar Excursion Module, the Saturn family of rockets (including the mighty Saturn V), Apollo perhaps did more than any over programme to shape NASA. It gave rise to the massive launch infrastructure at Merritt Island, Florida – now known as the Kennedy Space Centre – including the historic launch pads of Launch Complex 39, used by both Apollo and the shuttle, and now used by SpaceX and (soon) by NASA’s massive Space Launch System rockets; the Vehicle Assembly Building (then called the Vertical Assembly Building), where the Saturn rockets were assembled ready for launch, the still-used Launch Control Complex, and more. At the same time, Apollo gave NASA its operational heart for human space missions – the Manned Spaceflight Centre (now called the Johnston Spaceflight Centre) on land just outside Houston, Texas, donated to NASA by Rice University.

The entire history of the programme is a fascinating read – the politics, both in Washington (Kennedy’s own s science advisor, Jerome Wiesner, was quite vociferous in opposing the idea of sending men to the Moon) and in NASA (where a fierce difference of opinion was apparent in how the mission should be carried out. It’s a story I may some day plumb in a Space Sunday “special”, but for now I’ll simply say that all things considered, Apollo was a success, albeit one very self-contained. Six missions to the surface of the Moon, nine missions to and around the Moon, and the opportunity to increase our understanding of Earth’s natural satellite both by a human presence there and afterwards, thanks to the equipment left behind.

Armstrong, Collins and Aldrin pose for an official Apollo 11 crew shot, May 1st, 1969

New Horizons Pluto Flyby

July 14th marked the second anniversary of the New Horizons spacecraft’s flyby of Pluto and Charon – a high-speed dash between the two lasting mere hours, after a nine-and-a-half year flight simply to reach them. Brief though the encounter might have been, the spacecraft returned such a wealth of data and images that our view of Pluto and its companion has been forever changed, with Pluto in particular – as I’ve often referenced in these Space Sunday pieces –  revealing itself to be an enigma wrapped in a puzzle, determined to shatter our understanding of small planetary bodies in the solar system.

Such is the wealth of data gathered by the probe, coupled with the distances involved and the rate at which it could transmit data back to Earth, it took 16 months of all of the information stored aboard New Horizons to be returned to scientists here on Earth.

The July 14th mosaic of Pluto. The heart-shaped region is informally called “Tombaugh Regio” in honour of Pluto’s finder, Clyde Tombaugh. The left lobe of the “heart” is a vast icy plain. Credit: NASA/JHUAPL/SwRI.

To mark the second anniversary of New Horizons’ flyby, NASA released a new video using actual New Horizons data and digital elevation models of Pluto and Charon, to offer a unique flight across Pluto.

The movie starts over the highlands to the south-west of “Sputnik Planum’s” great nitrogen ice sheet (visible to the right as the movie progresses), with the track of the film passing directly over the chaotic cratered and mountain terrain of “Cthulhu Macula”. moving northwards, the flight passes over the fractured highlands of “Voyager Terra” then back southwards over Pioneer Terra, distinguished by pitting, before concluding over the bladed terrain of Tartarus Dorsa in the far east of the encounter hemisphere.

Continue reading “Space Sunday: anniversaries, storms and hidden worlds” →

Space Sunday: imaging a star and x-rays from a planet

Posted on by Inara Pey
The M-2 red super giant Betelgeuse, 650 light-years from Earth, as seen by the Atacama Large Millimetre Array (ALMA). Credit: ALMA / ESO / NRAO

Some call it Betelgeuse others call it Beetlejuice. It is the second brightest star in the constellation of Orion and officially designated Alpha Orionis, the ninth brightest star in the night skies over Earth.

A red super giant of spectral type M1-2, Betelgeuse is around 12 times the mass of our own Sun, and is one of the largest and most luminous stars visible to the naked eye. It is also destined to be – in cosmic terms –  very short-lived. At just eight million years of age, it is already approaching the end of its life and will likely go supernova some time in the next few thousand years.

But it is the star’s sheer size which makes it stunning: it’s an estimated 2.6 AU in diameter. To put this in perspective, were it to be dropped into our solar system to replace the Sun, it would extend out towards the orbit of Jupiter.  Such is its size, it is one of the few stars we can observe via telescope large enough to be resolved as anything more than a point of light.

This was brought home at the end of June 2017, when the Atacama Large Millimetre Array (ALMA) captured the star in a series of images taken at the sub-millimetre wavelength range. The images reveal the star’s chromosphere looking somewhat asymmetrical, the result of the star  generating a massive bow-shock as it moves through the interstellar medium. In short, as Betelgeuse travels through the gas clouds at a rate of around 30 kilometres per second, it own equivalent of the solar wind (much denser than anything the Sun generates) which is thrown off of the star at 17 kilometres / second, slams into this gas in the direction of travel at47 km/ sec, generating a massive shock wave about 3 light-years across in front of the star, which curls around it, influencing its chromosphere.

The bow shock preceding Betelgeuse, as seen by the Japanese Akari orbital observatory. Credit: JAXA/Akari

When Betelgeuse goes supernova, it will be in a blink of an eye – although we’ll only know about it 650 years after it has actually happened. When it does so, it will create an unmistakable light in the night sky – and this bow shock of matter will play a role in the supernova process, as it reacts to the sudden influx of matter slamming into it from the exploding star at a large fraction of the speed of light.

As violent as it will be, the Betelgeuse supernova will not threaten life on Earth, as it’s beyond the “harmful” range. And in case you think that’s a bit of a reach, scientists have shown that the Earth has in fact been influenced by supernovae in the past. This evidence comes from the presence of Iron 60 in the deep oceans, an isotope formed within stars, and which has an exceptionally short half-life: 2.6 million years – so the fact we can detect it suggests it originated in other stars that went supernova.

In fact, for the last 5-10 million years, the solar system has been travelling through a region of space called the “local bubble”, an expanding region of gases some 300 light years across, created by a series of supernova explosions which occurred over a relatively short period  of time about 20 million years ago. Within this bubble, the magnetic field is weak and disordered, which could greatly magnify the impact a large supernova occurring within 100 light years from Earth could have on life here.

At the upper end of this distance, research suggests a supernova could lead to climate changes similar to those which caused a rise in glaciation seen in the Pleistocene period, 2.5 million years ago. At the nearer end of this distance – say, 25-30 light years – a supernova could actually be an extinction level event for much of life here due to the radiation levels striking the Earth, altering the climate, impacting the Earth’s biomass, and giving raise to increases in cancers.

The stars of the IK Pegasi system compared to our own Sun (r). IK Pegasi is the large white star on the left, and IK Pegasi B – a potential supernova progenitor – is the white dot below and between the other two stars. Credit: R.J. Hall

Fortunately, the nearest known star to us which is likely to go supernova is IK Pegasi B, a massive white dwarf star which forms part of the binary star system IK Pegasi in the constellation of Pegasus, and 150 light years away. As a massive white dwarf, IK Pegasi is no longer generating energy through nuclear fusion. However, when its companion star, IK Pegasi A, a main sequence star slightly larger than our own Sun and itself a variable star, reaches the latter stages of its life, it will swell up to a red giant, allowing IK Pegasi B to star accrete matter from it, causing it to swell to as much a 1.4 solar masses – at which point it will explode as a supernova.

China’s Launch Failures

China’s space efforts have been in the news for the wrong reasons of late. In mid-June a Long March 3B rocket – the workhorse of the Chinese fleet – designed to carry a communications satellite to geostationary transfer orbit was declared a “partial failure” when the rocket’s upper stage failed, initially leaving the satellite stranded in a much lower orbit. Since then, mission controller have been using satellite’s manoeuvring motors gradually nudge it up to an operational orbit, although this will drastically shorten its active lifespan.

A slight fuzzy TV image of the Long March 5 launch on July 2nd, 2017. The vehicle suffered “an anomaly” shortly after lift-off and eventually crashed into the Pacific Ocean. Credit: CCTV

Then, on July 2nd, 2017, the second launch of China’s powerful Long March 5, capable of launching 8.4 tonnes of payload to the Moon or placing 25 tonnes in low Earth orbit, suffered a major failure shortly after clearing the launch pad at 11:23 GMT. This booster is key to China’s longer-term ambitions in space, as it is crucial to the development of their own space station, as well as vital for a number of deep space missions.

Continue reading “Space Sunday: imaging a star and x-rays from a planet” →

Space Sunday: 20 years on Mars, 24/7

Posted on by Inara Pey
On July 4th, 2017, we will have had a robotic presence at Mars 24/7 for twenty years. Here’s a look at those missions, and more. Credit: NASA/JPL

July 4th is a special date in American history, and this year it will, for space exploration enthusiasts be doubly meaningful, as it will mark the point at which we have been examining and exploring Mars continuously for 20 years without a single break.

Of course, attempts to explore and understand Mars began much earlier than that. We first started launching missions to the Red Planet far back in the 1960s. The first successful mission  – the United States’ Mariner 4 probe – shot past Mars in July 1965, returning just 22 fuzzy images as it did so, travelling too fast and without any fuel to achieve orbit. In 1969, and total overshadowed by the Apollo 11 mission to the Moon, Mariner 6 also flew by Mars in July, and was followed in August by its twin, Mariner 7, becoming the first dual mission to visit another world in the solar system.

Mariner 4’s route past Mars in July 1965, and the 22 images returned to Earth. Ironically, the vehicle flight path took it over some of the more “uninteresting” parts of Mars, leading some to dismiss it as being much the same as the Moon in looks. Credit: NASA

The first American mission to orbit Mars was Mariner 9, which arrived in orbit in November 1971, the exact time Mars was wreathed in a series of globe-spanning dust storms. Fortunately, the space vehicle had a planned orbital life of around 18 months, and successfully waited out the storms before returning the most spectacular images of Mars yet seen – including the mighty Tharsis volcanoes and the great gash of the Vallis Marineris, named in honour of the probe.

Russia also finally successfully reach Mars orbit in 1971 with the dual Mars 2 and Mars 3 missions. The former arrived just days after Mariner 9, and the latter became the first mission to successfully deploy a lander to the surface of Mars – although the craft ceased transmitting just 15 seconds after a safe landing had been confirmed, probably due to the dust storms. Unlike Mariner 9, the Russian orbiters had a shorter operational lifespan, and both ceased operations before the dust had fully cleared, resulting in them being classified as “partially successful” missions.

Then, in 1976 came the twin Viking Missions, comprising two pairs of orbiter and lander vehicles. Even now it remains one of the most ambitious robotic missions ever undertaken.  The Viking 1 orbiter and lander combination launched on August 20th, 1975 and arrived in Mars orbit on June 19th, 1976. Viking 2 departed Earth on September 9th, 1975 and arrived in Mars orbit on August 7th, 1976.

Viking returned the first colour still images of the surface of Mars, including this one, taken by Viking Lander 2, 1100 Sols into its mission and showing frost scattered over the ground before it. Credit: NASA/JPL

Viking Lander 1 had been scheduled to depart its orbiter and attempt a landing on Mars on July 4th, 1976 – the 200th anniversary of America’s independence. However, images of the landing site taken by the orbiter revealed it to be far rougher terrain than had been thought, so the landing was delayed while an alternative site was surveyed. The lander eventually touched-down on July 20th, 1976, marking the seventh anniversary of the first mission to land on the surface of the Moon. Viking lander 2 touched down half a world away on September 3rd, 1976.

Viking really was a landmark – and controversial – mission. Landmark, because they utterly changed our understand over Mars during years both orbiters and landers operated. Controversial because it is still argued to this day by some that two of the five life-seeking experiments carried by each of the landers did find evidence of Martian microbes living in the planet’s regolith, although it seems more likely that the positive results – in both cases, from the same two experiments – were the result of inorganic chemical reactions between mineral in the Martian soil samples and elements within the experiments.

After Viking the came a pause. While missions continued to be launched to Mars by the USA and Russia in the 1980s and early 1990s, none of them were successful. It was not until 1997 that the current trend of having vehicles continuously operating around and on Mars began – and which NASA has been celebrating, having been the stalwart of the 20-year effort of these 24/7 operations.

This run technically started in early November 1996, with the launch of NASA’s Mars Global Surveyor (MGS) mission. It was followed a month later by the NASA Pathfinder Mission. By a quirk of orbital mechanics, the Pathfinder Mission – designed to test the feasibility of placing a lander and small rover on Mars – arrived at Mars first, performing a successful aerobraking and landing on July 4th, 1996.

Mars Pathfinder being prepared in a clean room at NASA’s Jet Propulsion Laboratory. The lander’s base station in the centre of the vehicle and during flight would be surrounded by the three solar panel “petals”, one of which houses the Sojourner mini-rover, in its stored configuration. Credit: NASA/JPL

The Pathfinder lander arrived in Ares Vallis on Mars, an ancient flood plain in the northern hemisphere in an innovative way. A conventional aerodynamic heat shield protected the craft through initial entry into, and deceleration through, the upper reaches of Mars’ tenuous atmosphere. Having slowed from a velocity of several thousand kilometres an hour to just over 1300 km/h, allowing a supersonic parachute to be deployed. This slowed the vehicle’s descent to around 256 km/h and lowering the vehicle to just 355 metres above the surface of Mars, where several things happened.

Firstly, a tetrahedron cocoon of protective airbags was inflated all around the vehicle in less than a second. A set of rocket motors in the back shell beneath which the airbags and lander were suspended, then fired. These slowed the vehicle almost to a hover about 15-20 metres above the ground, at which point the tether connecting the cocooned lander was cut, and the lander fell to the ground, bouncing several times before coming to rest and the airbags were deflated and drawn back underneath the lander. The triangular lander was designed to right itself while unfolding its three solar power “petals”, however, this was not required as the lander came to a stop the right way up, allowing the petals to be deployed, and – after check-out tests – the little Sojourner rover was command to drive down off of the lander and onto the surface of Mars. The same system would later be used for the MER rover missions.

The Sojourner mini-rover on Mars during Sol 22 of its mission

As a proof of concept mission, Pathfinder was not intended to be a long duration mission. Just 65 cm (25.6 in) long and 48 cm (19 in) wide, the 10.5 kg (23 lb) Sojourner rover had a top speed of 1 cm a second, so it could never roam far from its base station;  in fact it never went further than about 12 metres (39 ft) from the base station, which acted as a communications relay as well as studying the Martian atmosphere and imaging Sojourner in action. Nevertheless, the mission exceeded expectations, lasting some 3 months, with the little rover examining 16 points of interest with its humble 0.3 megapixel cameras and its on-board spectrometer.

Continue reading “Space Sunday: 20 years on Mars, 24/7” →