Tag: Pluto

What you need to know about the Pluto flyby

The Wire
July 14, 2015

In under seven hours, the NASA New Horizons space probe will flyby Pluto at 49,900 km per hour, from a distance of 12,500 km. It’s what the probe set out to do when it was launched in January 2006. The flyby will allow it to capture high-resolution images of the dwarf planet’s surface and atmosphere as well as take a look at its biggest moon, Charon. For much of the rest of the day, it will not be communicating with mission control as it conducts observation. The probe’s Long-Range Reconnaissance Imager (LORRI) has already been sending better and better pictures of Pluto as it gets closer. During closest approach, Pluto will occupy the entire field of view of LORRI to reveal the surface in glorious detail.

Fourteen minutes into the Pluto flyby, New Horizons will make its closest approach to Charon, which is about 24,000 km away. Next: 47 minutes and 28 seconds after the Charon flyby, the probe will find itself in Pluto’s shadow where its high-gain antennae will make observations of how the dwarf planet’s atmosphere affects sunlight and radio signals from Earth as they pass through it. Then, 1 minute and 2 seconds after that, New Horizons will again be in sunlight. Finally, 1 hour and 25 minutes later, it will be in Charon’s shadow to look for its atmosphere.

That New Horizons survived the flyby will be known when, on early Wednesday morning (IST), it starts to send communication signals Earthward again. The timings of various events announced by NASA will have to be adjusted against the fact that New Horizons is 4.5 light-hours away from Earth. NASA has called for a press conference to release the first close-up images at 0030 hrs on July 16 (IST). The entire data snapped by the probe during the flyby will be downloaded over a longer period of time. According to Emily Lakdawalla,

Following closest approach, on Wednesday and Thursday, July 15 and 16, there will be a series of “First Look” downlinks containing a sampling of key science data. Another batch of data will arrive in the “Early High Priority” downlinks over the subsequent weekend, July 17-20. Then there will be a hiatus of 8 weeks before New Horizons turns to systematically downlinking all its data. Almost all image data returned during the week around closest approach will be lossily compressed — they will show JPEG compression artifacts. Only the optical navigation images are losslessly compressed. [All dates/times in EDT]

Downloading the entire science dataset including losslessly compressed observations will take until around November 2016 to complete. Until then, the best will always be yet to come. As always, all communications will be via the Deep Space Network – whose Goldstone base is currently all ears for the probe.

DSN Now. Source: Screengrab
DSN Now. Source: Screengrab

Incidentally, the ashes of the astronomer Clyde Tombaugh, who discovered Pluto in 1930, are onboard New Horizons.

What do we know about Pluto?

Among the last images taken by LORRI before the flyby revealed a strange geology on Pluto. Scientists noted dark and bright polygonal patches (in the shape of a whale and a <3, respectively) as well as what appeared to be ridges, cliffs and several impact craters. However, these features on the side of Pluto facing New Horizons as it flies in. During the flyby, it will image the other side of Pluto, where these features may not be present. The probe can’t hang around to wait to see the other side either because Pluto rotates once every 6.4 Earth-days.

An annotated image of Pluto snapped by the New Horizons probe. Credit: Applied Physics Lab/NASA
An annotated image of Pluto snapped by the New Horizons probe. Credit: Applied Physics Lab/NASA

During the flyby, images of Charon will also be taken. Already, the probe has revealed that, like Pluto, the moon also has several intriguing features – while until recently both bodies were thought to be frozen and featureless balls of ice and rock – like giant craters and chasms. In fact, NASA noted one crater near Charon’s south pole, almost 100 km wide and another on Pluto, some 97 km wide, both appearing to have been the result of recent impacts (in the last billion years). The particularly dark appearance of the Charon crater has two theories to explain it. Either the ice at its bottom is of a different kind than the usual and is less reflective or the ice melted during impact and then refroze into larger, less bright grains.

An annotated image of Charon snapped by the New Horizons probe. Credit: Applied Physics Lab/NASA
An annotated image of Charon snapped by the New Horizons probe. Credit: Applied Physics Lab/NASA

All these details will be thrown up in detail during New Horizons’ flyby. They will reveal how the two bodies evolved in the past, the structure and composition of their interiors, and if – for some astronomers – Charon might’ve harboured a subsurface ocean in its past. Complementarily, NASA will also be training the eyes of its Cassini, Spitzer and Keplerspace-borne instruments on Pluto. Cassini, from its orbit around Saturn, will take a picture of New Horizons just around the time of its flyby. From July 23 to July 30, the Spitzer Space Telescope will study Pluto in the infrared, mapping its surface ice. Then, in October, the exoplanet-hunting Kepler telescope, in its second avatar as K2, will start focusing on the changes in brightness off of and around Pluto to deduce the body’s orbital characteristics.

Then, there are also post-flyby missions whose results, when pieced together with the July 14 flyby and other observations, will expand our knowledge of Pluto in its larger environment: among the Kuiper Belt, at whose inner edge it resides.

Finally, as Dennis Overbye of The New York Times argued in a poignant essay, the Pluto flyby marks the last of the Solar System’s classical planets to explored, the last of the planets the people of our generation will get to see up close. The next frontiers in planetary exploration will be the exoplanets – the closest of which is 4.3 light-years away (orbiting Alpha Centauri B). But until then, be willing to consider the Solar System’s moons, missions to which are less than a decade away. Leaving you with Overbye’s words:

Beyond the hills are always more hills, and beyond the worlds are more worlds. So New Horizons will go on, if all goes well, to pass by one or more of the cosmic icebergs of the Kuiper belt, where leftovers from the dawn of the solar system have been preserved in a deep freeze extending five billion miles from the sun…

But the inventory of major planets — whether you count Pluto as one of those or not — is about to be done. None of us alive today will see a new planet up close for the first time again. In some sense, this is, as Alan Stern, the leader of the New Horizons mission, says, “the last picture show.”

Probe encounters glitch 10 days ahead of historic rendezvous with Pluto

The Wire
July 6, 2015

In the last mile of its 3,464-day journey and only ten days away from a historic rendezvous with the dwarf planet Pluto, the New Horizons probe experienced an anomaly on July 4 and prompted the on-board computer to switch to ‘safe mode’. The event caused a communications blackout between New Horizons and mission control at the Applied Physics Laboratory, Maryland, for 90 minutes on Saturday. Now, the probe is transmitting telemetry signals that will help scientists fix it – hopefully in time for its encounter with Pluto and its moons.

And until it’s fixed, science missions – including the detailed pictures it’s been taking of Pluto and Charon of late – will be on pause. Not surprisingly, the incident will have the scientists and engineers operating the probenervous. As Alan Stern, the mission’s principal investigator, said in June, “There’s only one Pluto flyby planned in all of history, and it’s happening next month!”

New Horizons was launched by NASA on January 19, 2006, with the primary objective of studying Pluto’s surface and atmosphere up-close, as well as observe its moons Charon, Nix, Hydra, Styx and Kerberos. In order to reduce mission costs at the time of launch, New Horizons was not designed to land on Pluto but to fly by it at a distance of about 13,000 km. On planetary scales, that’s small and excellent enough to fetch the dwarf planet out of the blur.

That historic flyby is supposed to happen on July 14. By then, the on-board anomaly needs to be recognized and fixed or the scientists, and humankind, risk losing years of efforts and patient waiting. Nonetheless, if the issue is fixed after the probe has flown past Pluto, it will still be used to study the Plutonian neighbourhood of which we know little. This is the region of space containing the Kuiper Belt objects, a belt of asteroids like the one between the orbits of Mars and Jupiter but over 20-times wider and denser. They comprise the matter leftover after the Solar System’s planets had formed.

According to Emily Lakdawalla, a planetary scientist affiliated with the Planetary Society, the probe is on the right trajectory even on the safe mode. She also wrote that there were no pictures set to be taken by the probe on July 4, but some on July 5 and 6 that might be missed.

Safe modes are not an uncommon occurrence on the computers operating satellites and probes, and even rovers. They are in effect similar to how a computer running the Windows OS sometimes slips into safe-mode, often to eliminate a bug that threatens some critical function, by reverting to a very primitive state conducive to troubleshooting.

In March 2013, the Curiosity rover on Mars entered into safe-mode following a computer glitch. In the next two days, its controllers transmitted the necessary code for the software running the rover to fix itself, and the rover was back online again. More recently, in April 2015, the Rosetta probe that’s tracking comet 67P/C-G went into safe-mode after its computer lost contact with radio signals from Earth, thanks to dust blown from the comet interfering with the antennae.

However, what makes the troubleshooting tricky is that New Horizons is 4.8 billion km away – a distance that radio signals take 4.5 hours to travel. This means the total time taken for mission control to send a message to New Horizonsand receive a reply is nine hours, and that the problem is likely to be fixed over the course of the next few days. Until then, let’s keep out fingers crossed.

Update: At 8 am (IST) on July 6, NASA put out a statement saying the problem in the computer had been resolved and that New Horizons would be able to revert to its original science plan on July 7.

The investigation into the anomaly that caused New Horizons to enter “safe mode” on July 4 has concluded that no hardware or software fault occurred on the spacecraft. The underlying cause of the incident was a hard-to-detect timing flaw in the spacecraft command sequence that occurred during an operation to prepare for the close flyby. No similar operations are planned for the remainder of the Pluto encounter.

It added that the down-time will have had a minor effect on the probe’s science objectives in the two days.

Pluto-bound probe takes first colour images of the dwarf planet and its moon

The Wire
June 22, 2015

A GIF of Charon orbiting Pluto compiled using images taken by the New Horizons MVIC Color Imager between May 29 and June 3, 2015. Credit: NASA
Credit: NASA

It may not look like much, but this heavily pixelated GIF image is cause for celebration. It effectively cost a robotic space probe more than nine years of travel and $600 million in manufacturing and operational charges. But then again, that’s not why the image is (and must be) celebrated. That privilege goes to the fact that these are the first colour photographs of our most adored dwarf planet. Say hello to an orangeish Pluto, being orbited by a grayish Charon.

Technically, it’s wrong to say Charon orbits Pluto – the two bodies were recently observed by the probe, New Horizons, to be orbiting a point in space called the barycenter. The barycenter is always closer to the larger body, so Pluto’s orbital radius is much smaller than Charon’s (as the GIF below shows).

A GIF showing Pluto and Charon in a binary system, compiled using images taken by the New Horizons MVIC Color Imager. Credit: NASA
A GIF showing Pluto and Charon in a binary system, compiled using images taken by the New Horizons MVIC Color Imager. Credit: NASA

As New Horizons gets closer to Pluto, its images will become sharper, affording humankind its first glimpse of the dwarf planet as it actually looks – not as imaginative illustrators have depicted it over the years. Alex Parker, a planetary astronomer at the Southwest Research Institute, Texas, had computed a “histogram of hues” in April 2015 showing that most people who didn’t use the correct reddish hue when depicting Pluto went for blueish hues.

On July 14, 2015, we’ll have the sharpest images to date of Pluto and Charon as New Horizons will make the first of its planned flybys, the manoeuvres it was built for, as it will study the atmosphere and surface characteristics of the bodies (here’s why it matters). The image resolution then will be down to a few kilometers. Astronomers can’t wait. On June 16, the National Space Society put out an anthemic video about the New Horizons mission, calling Pluto and its moons “the farthest worlds to be explored by humankind”.

Why you should care about the New Horizons probe nearing Pluto

The Wire
May 29, 2015

Alex Parker is a planetary astronomer at the Southwest Research Institute, Texas, and he posted his tweet just as I started writing this piece. And not just for Parker – it’s an exciting time for everyone, an exhilarating period in the history of space exploration. In just under 48 days – on July 14, 2015 – the NASA New Horizons space-probe will make its first fly-by of our favourite dwarf planet Pluto. Until then, it will be relaying less and less grainy pictures to Earth, each of more interest than the last, of a cold and distant world discovered by Clyde Tombaugh in 1930. One batch of images taken from May 8 to May 12 has already added to old evidence that Pluto hosts icy polar caps, and variations in surface brightness suggest a more uneven composition. On May 28, New Horizons restarted another phase of imaging – and as each day takes the probe 1.2 million km closer to its target, this is Pluto finally emerging out of the blur.

What more could we stand to find out? Quite a lot, as it turns out, from three points of view:

1. Toward the outer limits

The engineers operating the Voyager 1 space-probe (currently the farthest human-made object from Earth) had exciting news in September 2013: they claimed that about a year earlier, the probe had entered the interstellar medium – the space between stars, where the Sun’s influence was no longer the dominant one but had to contend with particulate emissaries from other stars in the galaxy. At the time, V1 was running on what little remained of its battery, a feeble ingot of blinking lights 19 billion km from Earth, and the occasion was replete with symbolism: humankind (or a representative) had set foot into the universe.

Actually, that moment could’ve transpired earlier. The engineers said that, in February 2012, the readings to indicate if V1 had entered the interstellar medium were spotted by the probe. However, they couldn’t be verified because the instrument that could do that had run out of juice. Luckily for them, a solar flare that erupted in March 2012 set the region of space around the probe thrumming with energy, which V1’s weak were able to pick up on and settle the matter.

Pluto, now, is much closer to the Sun than the threshold of the interstellar medium – in fact, the distance between Pluto and the Sun is 3.7 times smaller than the distance between Pluto and the medium. However, it is still quite far, and any space-probe sent to study it will either have to use up as little of its battery as it can until the rendezvous or be able to make only perfunctory observations of the dwarf planet. New Horizons is of the former kind – its primary mission is the farthest till date, and unlike the Voyager and Pioneer probes, will be able to respond to its environment agilely and be less susceptible to the vagaries of a dying battery.

2. Within the outer limits

Even if Pluto is among the outermost significant, planet-like bodies to orbit the Sun, it’s equally significant as being the largest body in the Kuiper Belt, a ring of asteroids like the one between the orbits of Mars and Jupiter. The belt starts from around the orbit of Neptune and extends to six AUs beyond the orbit of Pluto (AU is the astronomical unit, the distance between Earth and the Sun: 149.5 million km). It is also 200 times heavier than the Mars-Jupiter belt. Overall, both belts are important for two reasons in the context of New Horizons.

Before the Solar System took the form we now know – with a star at the centre, eight planets orbiting it, and two rings of asteroids – it comprised a young Sun at the centre of a massive disk of gases, dust and other materials called the protoplanetary disk. It is so named because it is out of this disk that the Solar System’s planets condensed, born as clumps of matter whose gravity accrued more matter, growing in size. And even as a planet formed, its gravitational pulls would ‘clean’ out a space in the protoplanetary disk, forming gaps. This phenomenon is visible among Saturn’s rings as well, with the space between rings having been cleaned out by the formation of small moons. The gaps in the disk survived to this day as the space between planets’ orbits. On the other hand, parts of the disk that didn’t get fully cleaned out formed the asteroid belts. So, they’re residues of the matter that the first planets were formed of, and studying them throws a lot of light on the history of the Solar System’s formation.

The second reason is that the asteroid belt between the orbits of Mars and Jupiter and the Kuiper Belt are separated by 4.2 billion km – even on the cosmological scale, that’s a non-trivial gap. However, many objects in the two belts share chemical and physical properties as if they were once part of a common larger body. One logical explanation is that the belts were ‘mixed’ after they were formed. And to explain such mixing, astronomers have an awe-inspiring yet plausible explanation. According to them, as Jupiter was forming, its orbits moved closer to the Sun and then farther away, before shrinking down to place it between the inner asteroid belt and Saturn. The increase and decrease in the orbit’s size could’ve been due to the formation of other planets in the system, which would’ve disrupted the gravitational equilibrium. And while Jupiter moved, its prodigious gravity could’ve tugged a part of the inner asteroids out and vice versa, resulting in a mixed composition of asteroids in both belts. Since Pluto is the largest among Kuiper Belt objects, New Horizons studying it in detail could provide more clues about if such mixing could’ve happened.

3. Beyond the outer limits

Pluto is all of 2,300-km across – the distance between Kanyakumari in south Tamil Nadu and New Delhi – and it has five moons all to itself: Nix, Styx, Hydra, Charon and Kerberos. All of them are Kuiper Belt objects, too, and astronomers are curious to know if Pluto has a ring system as well, populated by smaller asteroids. The dwarf planet will also likely have smaller rocks orbiting it, and dust particles kicked up as a result of collisions between them. Such dust will be dangerous for New Horizons because they could impact the probe at some 50,000 km/hr and damage on-board systems. In January 2014, Simon Porter, one of the probe’s mission scientists, had told Wired that to protect against such collisions, his team had a contingency plan in mind: to turn the probe’s 2.1-metre-wide dish antenna into a shield.

If the probe does make it through the danger zone and get to within 12,500 km of the surface of Pluto, its observations of any rings as well as the dwarf planet’s surface, atmosphere and any craters/seismic activity will reveal more about the composition of Kuiper Belt objects, how they interact with each other, whether they sport any signs of violence from the past, and if at all they have atmospheres, what they’re composed of – information important to understand how and where the Solar System’s other planets could’ve formed. Astronomers also already know that Pluto’s surface has frozen methane and carbon monoxide.

This and other data gleaned from Pluto and its surroundings will take until late-2016 to be transmitted to Earth but the probe’s journey will continue – rather, has to continue because a probe that’s gone so far might as well just go farther because of the considerable time taken to travel such distances. Because the primary mission will almost exhaust its battery, the probe will subsequently become less manoeuvrable – like the Voyager and Pioneer probes did, yet still boast of a sophisticated suite of instruments. To take advantage, astronomers from the Southwest Research Institute, including Alex Parker, had spotted three other Kuiper Belt objects in New Horizons‘ path in late 2014 that would be interesting to study. All three objects are about 30-55 km across and located about 44 AU from the Sun, meaning the probe will reach them around 2020. This timeline is very interesting because NASA plans to launch the James Webb Space Telescope – successor to the Hubble and Spitzer space telescopes – in 2018. The JWST will be better equipped to study the Kuiper Belt objects than Hubble is, and its observations could be complemented by New Horizons‘.

It is probably from all these expectations that the probe draws its promising name. There are parallels to be drawn between its (impending) exploration of Pluto and the Kuiper Belt, and the space beyond, and how astronomers look into the older universe. The speed of light in vacuum is the highest possible speed in the universe, so when astronomers train their telescopes to look billions of lightyears in one direction, they’re simply looking billions of years into our past. The farther a part of the cosmos is from us, the older the light from it is – and the older the information it is carrying is. A parallel of this ingrained association between space and time can be drawn with the distance New Horizons is travelling and the more than four billions years into our past it will be able to see. Here’s waiting with bated breath…