Category: Space Sunday

Orion: first flight time line

Posted on by Inara Pey
The moment of separation: Orion, shrouded by the Launch Abort System, and attached to the "dummy" Service Module / Delta upper stage combination at just after separation from the main stage of the Delta rocket. The two panels seen either side of Orion are the panel that protect the Service Module during ascent to orbit
The moment of separation: Orion, shrouded by the Launch Abort System, and attached to the “dummy” Service Module / Delta upper stage combination, just after separation from the main stage of the Delta rocket. The two panels seen either side of Orion protect the Service Module during ascent to orbit, and are jettisoned just ahead of the Launch Abort System

Update: Friday, December 5th. The Orion EFT-1 mission was a complete success, and I have an update available for those interested.

Update: Thursday, December 4th, 2014: due to a series of issues involving a boat straying too close to the launch pad, wind speeds around the pad exceeding safe limits, a fuel valve problem on two of the booster engines and – finally – concerns over the battery lief on Orion’s camera systems expiring due to lack of charge (with the fuel valve issues also unresolved) a decision was made to scrub the launch. A re-try will be made on Friday, December 5th, all major times given in the time line here remain the same, although NASA TV coverage will not commence until 11:00 UTC / 06:00 EST.

At approximately 12:05 PM UTC, on Thursday, December 4th, a Delta IV Heavy booster should lift-off from Launch Complex 37 at the Cape Canaveral Air Force Station (immediately to the south of NASA’s Kennedy Space Centre, and the home of the vat majority of America’s unmanned rocket launches).

Sitting at the top of the rocket, covered by the protective shroud of its Launch Abort System, will be America’s newest space vehicle, one that will – if all goes well, and political willingness is maintained – carry a crew to an asteroid in 2021, before taking humans back to the Moon, and then, perhaps around 2032, onwards to Mars and back.

The Orion "stack" at launch
The Orion “stack” at launch

The Orion Multi-purpose Crewed Vehicle (MPCV) is, as I’ve mentioned before in these pages, the first crew-capable space vehicle NASA has commissioned and will operate since the the space shuttle – a design itself rooted in the !970s. Yet in some respects, Orion evokes an even earlier era than that – the heady days of Apollo. Not only will it hopefully participate in lunar missions in the future, it actually resembles the Apollo Command Module, being a capsule vehicle, albeit one larger than Apollo (it can carry up to six crew, although four will likely be the usual crew number) and it is truly state-of-the-art in terms of design and capabilities.

This first launch will see Orion operated in an uncrewed proving flight, and will mark the start of a 4.5 hour mission that will see the capsule, complete with a “dummy” service module (again, like Apollo, Orion uses a Service module unit to supply life support, power and propulsion), travel further from the Earth than any vehicle designed to carry a crew has gone since the last of the Apollo Moon missions in 1972.

In doing so, the vehicle will be tested through the Van Allen radiation belts surrounding the Earth, and the capsule will be directed to re-enter the Earth’s atmosphere at around 80% of the velocity it would achieve on a return from a cislunar mission (that is, roughly 4,000 kph (2,500 mph) faster than the space shuttle ever returned to Earth).

For those interested in the mission, here’s a brief time line of events:

  • 03:50 UTC, December 4th / 10:50 EST, December 3rd: The mobile launch gantry starts to withdraw from the launch vehicle
  • 07:35 UTC / 02:35 EST, December 4th: Fuelling the Delta IV Heavy commences
  • 08:35 UTC / 03:35 ET: NASA flight control team take over from United Launch Alliance in managing launch preparations
  • 09:30 UTC / 04:30 EST: NASA TV coverage of the launch commences
  • 11:46 UTC / 06:46 EST: Terminal countdown hold for final pre-launch checks
  • 11:57 UTC / 06:57 EST: Go / No Go launch poll; Orion switches to internal power
  • 12::01 UTC / 07:01 EST:  Terminal countdown begins
  • 12:05 UTC: / 07:05 EST: Lift-off!
  • 12:05  through 12:22:39 UTC / 07:05 through 07:22:39 EST:  vehicle climbs to initial orbit of 185 x 888 kilometres (115 x 552 miles), during which boosters and first stage are jettisoned, as are the Service Module fairings and Launch Abort System. Orion and Service Module still attached to Delta upper stage
  • 14:00:26 UTC / 09:00:26 EST: Delta upper stage engine re-fires for 4:45 minutes, pushing the vehicle to its extended elliptical orbit that will carry it 5,800 km (3,600 miles) from Earth
  • 14:10-14:25 UTC / 09:10-0925 EST: Orion passes through Van Allen radiation belts; cameras turned off during this period
  • 15:10 UTC / 10:00 EST: Orion reaches furthest distance from Earth
  • 15:28:41 UTC / 10:28:41 EST: Orion capsule detaches from “dummy” service module / Delta upper stage
  • 15:35-16:10 UTC / 10:35-11:10 EST: Orions passes back through Van Allen radiation belts, reaction control motors used to initiate return to Earth
  • 16:18:35 UTC / 11:18:35 EST: re-entry into Earth’s atmosphere commences at 36,000 kph (20,000 mph)
  • 16:18:41-16:21:11 UTC / 11:18:41-11:21:11 EST: radio blackout & hottest period of re-entry with heat shield temperatures reaching 2,200C (4,000F), slowing the vehicle to around 480 kph (300 mph)
  • 16:24:29 UTC / 11:24:39 EST: parachute bay cover jettisoned (and also recovered after parachuting to its own splashdown)
  • 16:24:31 UTC / 11:24:31 EST: drogue parachute deployed, slowing vehicle from 480 kph (300 mph) to 160 kph (100 mph)
  • 16:25:40 UTC / 11:25:40 EST: main parachute deployed, slowing the vehicle from 160 kph (100 mph) to less than 30 kph (20 mph)
  • 16:28:29 UTC / 11:28:29 EST: Spashdown, to be followed by recovery by the USS Anchorage.
The boat (arrowed) that initially held the Thursday, December 4th launch, as it sits within the safety exclusion zone
The boat (arrowed) that initially held the Thursday, December 4th launch, as it sits within the safety exclusion zone. the first of several delays and issues which eventually resulted in the planned launch being scrubbed for 24 hours.

To infinity and beyond

Posted on by Inara Pey

Things are a tad quiet on the Mars news front, with Curiosity still on walkabout in the “Pahrump Hills”. So here’s a little round-up of some upcoming NASA news.

Orion Countdown

Thursday, December 4th should see the first launch of NASA’s next generation crewed space vehicle, the Orion Multi-purpose Crew Vehicle (MPCV). Superficially harking back to the days of the Apollo Moon landings, Orion is a two-stage vehicle comprising a capsule-like Command Module, capable of seating up to 6 astronauts, and a smaller Service Module, which supplies propulsion, power and life support. However, Orion is a lot more sophisticated than the Apollo craft, the capsule unit being a lot larger in both size and volume, and having the capabilities of both being reused and of making either a splashdown or landing on dry land on its return to Earth.

The Orions MPCV: an Apollo-like command module and, with its solar panels deployed, the Service Module
The Orion MPCV: an Apollo-like Crew Module and, with its solar panels deployed, the Service Module

As I’ve previously reported, this first launch of Orion will be uncrewed, serving to test the vehicle’s launch, flight and recovery capabilities in a mission lasting some 4.5 hours which will take the craft further from Earth than has been the case for any crewed vehicle since the last of the Apollo lunar missions in the 1970s. In doing so, the vehicle will be tested through the Van Allen radiation belts surrounding the Earth, and the capsule will be directed to re-enter the Earth’s atmosphere at around 80% of the velocity it would achieve on a return from a cislunar mission (that is, roughly 4,000 kp/h (2,500 mph) faster than the space shuttle ever returned to Earth).

Orion is designed to sit at the hub of NASA’s plans for the initial human exploration of the solar system. Its likely future uses include ferrying crews to the Moon and back and, in the 2030s, forming the command vehicle in a human mission to Mars.

An artist's conception of Orion delivering a large lunar lander to the Moon
An artist’s conception of Orion delivering a large lunar lander to the Moon

For lunar missions, Orion will, again like Apollo, be mated to a lunar lander, which it will ferry to the Moon, before the crew transfer to the lander and descend to the Moon’s surface. Again, the differences are that with the Orion mission, the MPCV can remain “parked” in lunar orbit unattended while the crew use their lander and equipment and facilities landed remotely on the Moon to spend weeks or Moons there, rather than days.

For missions to Mars, Orion will be part of a much larger vehicle, the details of which are still to be decided, but which is likely to be launched by Orion’s dedicated rocket, the Space Launch System (SLS), in a number of parts which will rendezvous in orbit prior to the crew flying to it via Orion and embarking. An Orion capsule would then serve as the Crew Return Vehicle, delivering the crew back to Earth at the end of there 3-year mission.

An Orion would serve as the Crew Return Vehicle to deliver the crew safely back to Earth at the conclusion of a nuclear-powered mission to Mars (NASA Design Reference Architecture mission)
An Orion would serve as the Crew Return Vehicle to deliver the crew safely back to Earth at the conclusion of a nuclear-powered mission to Mars (concept: NASA Design Reference Architecture mission)

Orion’s first mission will use a fully-functional capsule mated to a “dummy” service module (the actually service module is to be built by the European Space Agency, using the technologies developed in the hugely successful but grossly under-sung Automated Transfer Vehicle design, which has been quietly resupplying the International Space Station for the last five years (and refuelling it) with up to 7 tonnes of supplies per flight – more than double anything managed by the Russian Progress supply vehicles, the SpaceX Dragon and Orbital Science’s Cygnus vehicle.

In 2017, Orion will make an unmanned flight around the Moon (shown in the video below), this time using an actual Service Module and the SLS launcher, in what is being called the Exploration Mission 1. Then, in around 2021, Orion will fly its first crew in a mission to rendezvous and land on an asteroid.

New Horizons to Wake-up

Assuming all goes according to plan, two days after the Orion test flight, over 26 AU from Earth (AU being an astronomical unit – the average distance between the Earth and the Sun – that’s 149,597,871 kilometres or 92,955,807 miles), a tiny space craft will “wake up” from the third of three hibernation periods which have collectively lasted 31 months, allowing it to ready itself for its primary mission objective: a 6-month “flyby” of the dwarf planet Pluto, which should yield masses of information about that world and its major companion Charon.

after 10 years in space – the last 31 months of which have been largely in hibernation (other than brief periods of science data gathering), and a voyage through our solar system which has, like that of ESA’ comet-chasing Rosetta mission – provided many other opportunities for science discovery, New Horizons will commence its primary mission in January 2015, as it starts into its approach and fly-past of Pluto, Charon and their family of tiny “moons”, Kerberos, Styx, Nix and Hydra.

An artist's impression of New Horizon passing Pluto, with Charon and the Sun behind.
An artist’s impression of New Horizon passing Pluto, with Charon and the Sun behind.

No-one actually knows what New horizons will reveal; such is the distance between Earth and Pluto, we know very little about it in real terms, so the mission is very much like those of the pioneering days of space exploration, when we sent vehicle to Venus and Mars, not actually knowing for sure what they’d find.

Despite travelling at 1,600,000 kilometres a day, it will take New Horizons until July 2015 to reach its point of closest approach to Pluto – just 10,000 kilometres from the planet’s surface. The images and data it should return to Earth promise to be astounding.

And after July 2015? New Horizons will be heading out into deep space beyond our solar system, becoming only the third vehicle built by humans to do so, the other two being Voyagers 1 and 2. Providing it is still active, New Horizon should reach the heliosphere,  the “boundary layer” marking the divide between the solar system and interstellar space, in 2038. Between 2015 and then, the craft will be used to observe other Kuiper belt objects of interest and send back data on the space through which it is travelling.

Wanderers

Whether humanity ever joins Voyager and New Horizons in moving beyond our own solar system is a subject of popular debate. Given the distances involved between the stars, the only practical way of reaching solar systems beyond our own in through exotic methods – faster-than-light travel, wormholes, and the like – if we are to avoid centuries and generations travelling the interstellar void; and there is still no guarantee we’ll harness either.

But even should we remain locked inside our own solar system for centuries to come, we still have a vast range of environments to explore and possibly tame. This is something Erik Wernquist reminds us about in a stunning video he’s produced, using selected commentary spoken by the great Carl Sagan during his ground-breaking television series, Cosmos. This really is one to watch.

My thanks to Nalates Urriah for pointing me to Erik’s video.

Of Martian walkabouts, pictures from a comet, and getting ready to fly

Posted on by Inara Pey

CuriosityIn my last report on the Mars Science Laboratory, I mentioned that Curiosity has been on a geology “walkabout” up the slopes of the “Pahrump Hills” at the base of “Mount Sharp” (more correctly, Aeolis Mons). The zigzagging route up through the area took the rover from “Confidence Hills” and the location of the last drilling operation up to a point dubbed “Whale Rock”, the drive being used to gather information on potential points of interest for further detailed examination.

The exposed rocks in this transitional layering between the floor of Gale Crater, in which Curiosity arrived back in August 2012, and the higher slopes of “Mount Sharp” is expected to hold evidence about dramatic changes in the environmental evolution of Mars. Thus, the “walkabout”  – a common practice in field geology on Earth – was seen as the best means of carrying out a reasonable analysis of the area in order for the rover to be most efficiently targeted at specific locations of interest.

Curiosity’s walkabout, from “Confidence Hills” to “Whale Rock” in October, the rover is now working its way back to various points of interest for further studies

“We’ve seen a diversity of textures in this outcrop,” Curiosity’s deputy scientist Ashwin Vasavada (JPL) said of the drive. “Some parts finely layered and fine-grained, others more blocky with erosion-resistant ledges. Overlaid on that structure are compositional variations. Some of those variations were detected with our spectrometer. Others show themselves as apparent differences in cementation or as mineral veins. There’s a lot to study here.”

During the drive, Curiosity travelled some 110 metres, with an elevation of about 9 metres, using the Mastcam and the ChemCam (Chemistry and Camera) laser spectrometer system to inspect and test potential points of interest for more detailed examination at a later date. Since completing that drive, the rover has been working its way back through Pahrump Hills, this time examining specific targets using the robot-arm mounted Mars Hand Lens Imager (MAHLI) camera and spectrometer. Once this work has been completed, specific targets for in-depth analysis, including drilling for samples will for the core activity of a third pass through the area.

So far, two specific areas have been identified for detailed examination. The first, dubbed “Pelona” is a  fine-grained, finely layered rock close to the “Confidence Hills” drilling location. The second is a small erosion-resistant ridge dubbed “Pink Cliffs” the rover drove around on its way up the incline.

“Pink Cliffs” is roughly a metre (3ft) in length and appears to resist wind erosion more than the flatter plates around it.As such, it offers precisely the kind of mixed rock characteristics mission scientists want to investigate in order to better understand “Mount Sharp’s” composition. This image is a mosaic of 3 pictures captured on October 7th PDT, 2014 (Sol 771 for the rover) by Curiosity’s Mastcam. It has been white balanced to show the scene under normal Earth daylight lighting – click for full size.

Another target of investigation has been the edge of a series of sand and dust dunes right on the edge of “Pahrump Hills”.  In August 2014, Curiosity attempted to use these dunes as a means to more quickly access the “Pahrump Hills” area, but the effort had to be abandoned when it proved far harder for the rover to maintain traction than had been anticipated, particularly given the rover has successfully negotiated sandy dunes and ridges earlier in the mission. As a result, scientists are keep to understand more about the composition of the dunes.

On November 7th, Curiosity was ordered to venture onto the dunes very briefly in order to break the surface of one of the rippled dunes and expose the underlying layers of sand in an effort to better understand why the rover found the sand such hard going the first time around, and what might be within these wind-formed dunes that would prove to be so bothersome to driving over them. Data gathered from the drive is still being analysed.

Spanning roughly 1.2 metres from left to right, a wheel track breaks the surface of a dust sand dune ripple on the edge of “Pahrump Hiils”. The MSL science team hope the exposed material within the ripple will help them understand why Curiosity found these dunes hard-going when trying to cross them in August 2014.

The work in the “Pahrump Hills” area has given rise to concerns over one of the two lasers in the ChemCam instrument. As well as the main laser, known for “zapping” targets on the surface of Mars in order to reveal their chemical and mineral composition, the system uses a second laser, a continuous wave laser, used for focusing the ChemCam’s telescope to ensure the plasma flash of vaporised rock is properly imaged when the main laser fires. Data received on Earth when using the ChemCam to examine rocks on the first pass through “Pahrump Hills” suggests this smaller laser is weakening and may no longer be able to perform adequately.

If this is the case, the laser team plan to switch to using an auto-focus capability with the telescope so it will automatically focus itself on a few “targeting” shots from the main laser ahead of any data-gathering burst of fire, allowing for proper telescope calibration.

Continue reading “Of Martian walkabouts, pictures from a comet, and getting ready to fly” →

The little lander that could – and did

Posted on by Inara Pey
Rosetta,
Rosetta,Philae and, behind them, comet 67P/Churyumov–Gerasimenko seen in an artist’s impression of the mission

It’s been a hectic 48 hours. On Wednesday, November 12th, after 10 years in space, travelling aboard its parent vehicle, Rosetta, the little lander Philae touched down on the surface of comet 67P/C-G/Churyumov–Gerasimenko (67P/C-G). It was the climax of an amazing space mission spanning two decades – and yet was to be just the beginning. Packed with instruments, it was hoped that Philae would immediately commence around 60 hours of intense scientific investigation, prior to its batteries discharging, causing it to switch to a solar-powered battery system.

Unfortunately, things haven’t quite worked out that way. As I’ve previously reported, the is very little in the way of gravity on the comet, so in order for Philae to avoid bouncing off of it when landing, several things had to happen the moment it touched the comet’s surface. As it turned out, two of these things didn’t happen, with the result that the lander did bounce – twice.

Where Philae may be (ESA image via BBC News) – Rosetta has yet to positively locate the lander beyond a rough estimate based on communications and signals received from the CONSERT instrument on the lander

The first time it rose to around 1 kilometre above the comet before descending once more in a bounce lasting and hour and fifty minutes, the second time it bounced for just seven minutes. Even so, both of these bounces meant the lander eventually came to rest about a kilometre away from its intended landing zone. What’s worse, rather than touching down in an area where it would received around 6-7 hours of sunlight a “day” as the comet tumbles through space, it arrived in an area where it was only receiving around 80-90 minutes of sunlight – meaning that it would be almost impossible to charge the solar-powered battery system.

As noted above, the mission was designed so that most of the core science could be carried out in the first 60 hours of the mission, just in case something like this occurred. Even so, in order to prolong the life of the vehicle, it would have been nice to move it into a greater area of sunlight. A means of doing this had also been built-in to Philae: the three landing legs can be flexed, allowing it to “hop”. But as images were returned to Earth by the Lander, it became apparent that one of the legs is not in contact with the ground, making such a hop problematic. After discussion, it was decided not to attempt to move the lander, but focus on trying to achieve the planned science objectives.

In this image released by ESA, a model of the Philae lander has been superimposed on images of the vehicle's shadowy surroundings as captured by the panoramic cameras mounted around the lander (image: Image: Sipa USA/Rex)
In this image released by ESA, a model of the Philae lander has been superimposed on images of the vehicle’s shadowy surroundings as captured by the panoramic cameras mounted around the lander (image: Image: Sipa USA/Rex)

As it turned out, the initial contact between the lander and the comet confused several of Philae’s instruments into “thinking” it had in fact landed, causing them to activate. These included the ROMAP magnetic field analyser, the MUPUS thermal mapper, the CONSERT radio sounding experiment and the SESAME sensors in the landing gear. Data received from these instruments, arriving on Earth some 30 minutes after initial contact with the comet, and the information which followed, help alert mission staff that something had gone wrong, and enabled them to subsequently piece together the events that occurred during the landing sequence, while the instruments continued to gather data and transmit it back to Earth via Rosetta.

On Friday, November 14th, the decision was taken to activate Philae’s sample-gathering drill, officially referred to as SD2. This had been postponed from the previous day, as the drill uses a lot of power. However, obtaining and analysing samples from inside the comet is a central part of the mission, the decision was made to push ahead with drilling operations.

Continue reading “The little lander that could – and did” →

Philae: “I’m here, not there!”

Posted on by Inara Pey
The first image from the surface of a comet, returned to Earth by the Rosetta lander Philae, November 13th, 2014. image: ESA/Rosetta/Philae/CIVA
The first image from the surface of a comet, returned to Earth by the Rosetta lander Philae, November 12th, 2014. image: ESA/Rosetta/Philae/CIVA

Wednesday, November 12th saw a remarkable feat take place over 515,000,000 kilometres from Earth as a small robotic vehicle called Philae, and a part of the European Space Agency’s Rosetta mission, landed on the surface of a comet, marking the very first time this has ever been achieved.

As I reported, immediately following the landing, getting a vehicle to rendezvous with a comet, enter orbit around it and deploy a lander to its surface isn’t easy – Rosetta is a mission 21 years old, with the spacecraft spending a decade of that time flying through space.

Mission control personnel react to the first telemetry received from Philae on it's initial contact with the surface of comet 67P/C-G
Mission control personnel react to the first telemetry received from Philae on its initial contact with the surface of comet 67P/C-G

Immediately following the landing, telemetry revealed things hadn’t gone to plan, although the lander itself was unharmed. Essentially, part of the landing system – a pair of harpoons designed to tether the lander to the comet’s surface as a direct result of the very weak gravity there – failed to operate as expected. Telemetry has shown that the tensioning mechanism and the harpoon activation process started, but the harpoons themselves did not fire. As a result, the vehicle actually “bounced” after its initial touch-down.

The initial touch-down was at 15:33 UT – precisely on schedule and on target. However, as the harpoons failed, the lander rose back up – possibly by as much as a kilometre – above the comet, before finally striking the surface again, two hours later. This means that even while celebrations over the initial landing were going on here on Earth (the initial signal confirming touchdown taking some 30 minutes to reach Earth), Philae had yet to make its second contact with the comet.

Philae (circled in red) en route to its landing site on 67P/C-G (visible top right)
Philae (circled in red) en route to its landing site on 67P/C-G (visible top right)

This eventually happened at 17:26 UT, and was followed by another bounce, this one of a much lesser force, before the lander came to rest at 17:33 UT.

One of the consequences of this bouncing is that the lander is not actually in its designated landing zone – the comet is tumbling through space, and thus turning under the lander as it bounced. This means that while Rosetta and Philae are communicating with one another, the spacecraft’s orbital position around the comet is not optimal for the lander’s position, and is being refined to better suit Philae’s new location. An initial adjustment was made overnight on the 12th/13th November, and further adjust is likely to be made on Friday, November 14th. Currently, communications can occur between the two vehicles for just under 4 hours out of every 13.

Philae mission manager Stephan Ulamec explains where it is belived the lander resides, represented by the blue triangle (ESA press conference, Thursday, November 14th)
Philae mission manager Stephan Ulamec explains where it is believed the lander resides, represented by the blue triangle (ESA press conference, Thursday, November 14th)

This bouncing may explain why there was an initial problem with communications between the lander and the Rosetta spacecraft, as reported immediately after the initial landing telemetry was received: Rosetta was expecting Philae to be at a certain fixed position on the comet, whereas the lander was still in motion, and “moving away” from the landing site as the comet rotated. The task now is for Rosetta to visually locate the lander – which given the current orbital positioning, may take a little time; the next passage of the spacecraft over the region of the landing site will not start until 19:27 UT this evening. Mission planners hope the sunlight reflected by the lander’s solar panels might help in identifying Philae’s exact position.

A core worry for the mission team is that Philae has in fact come down in an area of shadow, possibly in a depression and close to one or two rocky “walls”, and it appears to only be receiving direct sunlight for around 90-120 mins as the comet tumbles, rather than the 6-7 hours planned with the target landing point. This potentially has serious implications for the lander’s power and science regime, although it is hoped that Philae might be able to adjust its position somewhat – the craft actually has the capability of “hopping” around by flexing its landing legs.

Continue reading “Philae: “I’m here, not there!”” →

To touch the origins of the solar system

Posted on by Inara Pey
Brave new world: the surface of comet 67P/C-G, upon which the European space Agency successfully landed a the robot vehicle Philae on Wednesday, November 12th, 2014 as a part of the Rosetta mission
Brave new world: the surface of comet 67P/C-G, upon which the European space Agency successfully landed a the robot vehicle Philae on Wednesday, November 12th, 2014 as a part of the Rosetta mission

“The biggest problem with success is that it looks easy, especially for those of us who have nothing to do.” Thus spoke Jean-Jacques Dordain on Wednesday, November 12th, just moments after it had been confirmed that a tiny robot vehicle called Philae had safely landed on the surface of a comet half a billion kilometres away from Earth.

That simple statement offers a subtle message on the huge achievement this landing represents. The Rosetta / Philae mission is the story of a 6 billion kilometre journey across space which has taken a decade to achieve, and which has involved some 20 countries. Yet the adventure is in many ways only now starting.

The Rosetta mission actually started 21 years ago, in 1993 when it was approved as the European Space Agency’s first long-term science programme. The aim of the mission being to reach back in time to the very foundations of the solar system by rendezvousing with, and landing on, a comet as it travel through the solar system.

An artist’s impression of Rosetta in space. It has already achieved a remarkable set of “firsts”, including the first solar-powered space probe to operate beyond the orbit of Mars. Philae, the lander, is the purple house shape on the front of the vehicle

Comets hold enormous scientific interest because they are, as far as can be determined, the oldest, most primitive bodies in the Solar System, preserving the earliest record of material from the nebula out of which our Sun and planets were formed. While the planets have gone through chemical and (in the cases of places like Earth), environmental and geological change, comets have remained almost unchanged through the millennia. What’s more, they likely played an important role in the evolution of at least some of the planets. There is already substantial evidence that comets probably brought much of the water in today’s oceans – and they may even have provided the complex organic molecules that may have played a crucial role in the evolution of life here.

The target for ESA’s attention is comet 67P/Churyumov–Gerasimenko (aka 67P/C-G), an odd-shaped body comprising two “lobes” joined together one  in what some in the media have at times referred to as the “rubber duck”. The larger of the two lobes measures some 4.1×3.2×1.3 kilometres in size (2.55×1.99×0.8 miles) and the smaller some 2.5×2.5×2 kilometres (1.6×1.6×1.2 miles). It is a “short period” comet, orbiting the Sun once every 6.4 years and most likely originating in the Kuiper belt, a disk of material from the early history of the solar system, orbiting the Sun at a distance of around 30-50 AU

The primary spacecraft in the mission, Rosetta, arrived in the vicinity of 67P/C-G on August 6th, 2014 becoming the first vehicle in history to successfully enter orbit around a comet. The major reason the mission took so long to reach the comet, having been launched in 2004, is that despite having a relatively short orbital period, 67P/C-G is travelling very fast and accelerating as is falls deeper into the Sun’s gravity well heading for perihelion (it is currently travelling at 18 kilometres (11.25 miles) a second and can reach velocities of 34 kilometres a second as it swings around the Sun). As it is impossible to launch a space vehicle is these velocities, Rosetta was launched on a trajectory which allowed it to fly by Earth twice (2005 and the end of 2007) and Mars once (early 2007), using the gravity of both planets to accelerate it and (in the case of the 2nd Earth fly by), swinging it onto an orbit where it would “chase” and eventually catch the comet.

It’s a long way from here to there: Rosetta’s flight from Earth to 67P/C-G (image via extremetech.com) – click for full size

Following its safe arrival, Rosetta settled into an orbit of some 30 kilometres around the comet in September, and began looking for a suitable place where Philae might land – because until the craft actually arrived in orbit around 67P/C-G, no-one had any idea of what it’s surface might look like. On 15 September 2014, ESA announced a region on the “head” of the “duck” had been selected for the landing, christening it Agilkia in keeping with a contest to name the landing site.

Further observations of the comet were carried out throughout September and October as an overall part of Rosetta’s mission and to gain as much information on the landing site itself. At the same time the spacecraft started manoeuvring itself in closer to the comet, dropping its orbit to just 10 km, ready for Philae’s delivery.

This image, captured by Rosetta on Wednesday, November 12th, shows the Philae lander as it starts its descent towards the comet
This image, captured by Rosetta on Wednesday, November 12th, shows the Philae lander as it starts its descent towards the comet

The landing operations commenced around 09:05 UT on Wednesday, November 12th, when Philae detached from Rosetta and started on its long gentle descent. Immediately following the separation, and due to Rosetta’s orbit around the comet, contact was almost immediately lost with the lander, leading to a tense 2 hour wait before communications could be re-established. This happened on cue, with the lander reporting all was OK.

Landing on a comet is no easy task. The gravity is almost non-existent, and there was a very real risk that Philae could, if it struck the surface of 67P/C-G too fast, simply bounce off. Hence the lander’s long, slow drop from the Rosetta spacecraft which the ESA mission scientists dubbed “the seven hours of terror” in recognition of the famous “seven minutes of terror” which marked the arrival of NASA’s Mars Science Laboratory Curiosity on Mars.

Continue reading “To touch the origins of the solar system” →