New Horizons • Mission Plan

Designing a spacecraft and mission plan to explore the vicinity of Pluto is made difficult by many factors. Not least of these is the time it will take to get there .. without playing orbital tricks and stealing energy from other objects orbiting the Sun, getting to Pluto would take nearly twenty years.

Interplanetary flights, until the last few years, have relied on giving a spacecraft a speed boost as it leaves the the Earth. That extra velocity allows the spacecraft's path to diverge from the Earth’s, either drifting outward to Mars, Jupiter, Saturn, etc, or drifting inwards to Venus or Mercury.  It is surprising, perhaps, that getting an object to Mercury requires extraordinary measures to slow it down enough to get there. But New Horizons had the other problem, gaining energy to raise its orbit so it would reach forty times further from the Sun than the Earth, and still be traveling fast when it got there. In fact, New Horizons, like the long-range Pioneer and Voyager spacecraft before it, will never return.

Even with the most powerful rocket available, the trip to Pluto would take too for long for electronic and mechanical systems to remain reliable by the time Pluto was close enough to observe, but celestial mechanics give us a gift of time. If launched at the highest possible velocity in the last two weeks of January 2006, New Horizons could pass Jupiter just in time to use that planet's massive gravity to accelerate it to a speed that would hurl it to Pluto's orbit in about nine years. That favorable alignment happens every year if all you want to do is travel 35-45AU in a decade; if you want that trajectory to put you there when Pluto is nearby, that chance comes only a very few times every 250 years. The next "launch window" opened in early February 2007, but that delay would add three years to the flight time.

So on January 19, 2006, New Horizons was launched on an augmented Atlas-Centaur three stage rocket (NASA's most powerful at the time), and was the fastest spacecraft ever to leave the Earth. It passed the distance of the Moon in a nine hours (most flights to the Moon last more than three days), and it reached Jupiter in thirteen months.

The science instruments, cameras, fields and particle detectors, nine instruments in all, are the reason to fly, but the engineering systems to deliver them to the right place, power them, point them in the right direction, keep them warm, and transmit their data back to the home plant are pretty critical too. Spacecraft design and construction is a constant well-managed battle between science and engineering! New Horizons weighed about 480Kg at launch; about 30Kg was science instruments.

Fuel for course correction and pointing accounts for about 75Kg of that; It carries a 210cm dish antenna on its back and, since it will be too far from the Sun for solar cells to work, it also carries a 200watt radioisotope thermoelectric generator (RTG). At Pluto its fastest data transmission rate will be 700 bits/second, and it will take nine months to dump the entire "Pluto Encounter" dataset back to Earth.

Once past Jupiter, New Horizons was placed in 'hibernation mode' which it mostly remained in (woken every year for a system check) till three weeks ago when it was woken to start preparations for Pluto. Pluto "far encounter" starts on January 15, when distant imaging of Pluto against the starry background (for navigation), and other measurements of the interplanetary environment are begun.

New Horizons • Pluto

2015 will be a special year for interplanetary exploration. By the end of the 1970's, humans had sent spacecraft to every planet in the Sun's family, except one.  Missions to orbit Mercury, Venus, Mars, Jupiter and Saturn, and to land four rovers on Mars, have followed. More recently, many of the lesser objects in the solar system have been studied up close: asteroids, the moons of Jupiter and Saturn, and even comets.

In 1930, Pluto was discovered by Clyde Tombaugh, working at the Lowell Observatory in Flagstaff, Arizona. Much smaller than the Earth's Moon, Pluto was found nearly one and a half billion Kilometers beyond Neptune. Pluto has always been been an emigma, its orbit dips inside Neptune's for part of its year and is tipped out of the plane of the other planets, its polar axis is tilted by nearly 90 degrees, its biggest moon, Charon, is about the same size as it is.

In fact, Pluto isn't a planet like the others, it's a member of the Kuiper Belt of objects which has strayed down into the outer regime of the regular planets. The Kuiper Belt represents a cloud of material that never joined in the serious planet making beginnings of the solar system .. some clumping of rocky and icy material happened, but probably none of the violence of melting, bombardment, destruction and collisions that created the inner planets, or the immense gravitational influences that pulled Jupiter, Saturn, Uranus and Neptune into gaseous giants. The Kuiper Belt has been called the dust bunny collection of the solar system.

Following the discovery of more Kuiper Belt objects (KBO's) by Hubble and other powerful telescopes, Pluto joined the new designation of 'dwarf planets' in 2006. Arguments revolve about this reclassification but Pluto is now in a class containing more named objects than there are classical planets (and there are hundreds more observed candidates for the class awaiting confirmation of their orbits and naming).

But Pluto remains unexplored, and enigmatic, to this day. Telescopic instruments have improved since Tombaugh's day; but even the Hubble Space Telescope can magnify the faint point of light that is Pluto barely enough to image it as a fuzzy disk. The HST has also observed four small moons (Nix, Hydra, Kerberos and Styx) in addition to Charon. Pluto is rocky and has a thin atmosphere (mostly nitrogen) that freezes, falling like snow, for the Plutonian 'winter'.

[Pluto takes about 250 years to orbit the Sun. It swings in to about 30AU (closer than Neptune) for some of that time getting close enough to heat its atmosphere into a gas, then back out to about 50AU for a century and a half cold spell. This extreme orbital swing has more impact on Pluto's temperature that its seasons .. because its rotational axis is so tilted, Pluto's "arctic circle" is, essentially, its equator!  Pluto's south pole saw the sun for the first time in 120 years in 1987. Just to completely remove it from your list of vacation spots, the temperature of the surface is 35-55 degree above absolute zero.] -- 1AU (Astronomical Unit) is the distance from the Sun to the Earth ~ 150 million Km.

Planning for a mission to Pluto began in 1989, and the New Horizons spacecraft was launched in January 2006. It will fly though Pluto's space (about 10,000Km above its surface) on July 14, 2015. Recently, after a long search, another KBO was found by Hubble, far beyond Pluto, but reachable, with little expenditure of fuel, by New Horizons in 2019.

Endeavour and ISS -- Last time ?

This morning at 4:50am shuttle Endeavour and the ISS, separated but too close to tell without binoculars.

GRB 080319B - March 19, 2008 at 02:13 EDT

RELEASE: 08-223

"NAKED-EYE" GAMMA-RAY BURST WAS AIMED SQUARELY AT EARTH

WASHINGTON -- Data from satellites and observatories around the globe show a jet from a powerful stellar explosion witnessed March 19 was aimed almost directly at Earth.

NASA's Swift satellite detected the explosion - formally named GRB 080319B - at 2:13 a.m. EDT that morning and pinpointed its position in the constellation Bootes. The event, called a gamma-ray burst, became bright enough for human eyes to see. Observations of the event
are giving astronomers the most detailed portrait of a burst ever recorded. "Swift was designed to find unusual bursts," said Swift principal investigator Neil Gehrels at NASA's Goddard Space Flight Center in Greenbelt, Md. "We really hit the jackpot with this one."

In a paper to appear in Thursday's issue of Nature, Judith Racusin of Penn State University and a team of 92 coauthors report on observations across the spectrum that began 30 minutes before the explosion and followed its afterglow for months. The team concludes the burst's extraordinary brightness arose from a jet that shot material directly toward Earth at 99.99995 percent the speed of light.

At the same moment Swift saw the burst, the Russian KONUS instrument on NASA's Wind satellite also sensed the gamma rays and provided a wide view of their spectral structure. A robotic wide-field optical camera called "Pi of the Sky" in Chile simultaneously captured the
burst's first visible light. The system is operated by institutions from Poland.

Within the next 15 seconds, the burst brightened enough to be visible in a dark sky to human eyes. It briefly crested at a magnitude of 5.3 on the astronomical brightness scale. Incredibly, the dying star was 7.5 billion light-years away.

Telescopes around the world already were studying the afterglow of another burst when GRB 080319B exploded just 10 degrees away. TORTORA, a robotic wide-field optical camera operated in Chile with Russian-Italian collaboration, also caught the early light. TORTORA's
rapid imaging provided the most detailed look yet at visible light associated with a burst's initial gamma-ray blast.

Immediately after the blast, Swift's UltraViolet and Optical Telescope and X-Ray Telescope indicated they were effectively blinded. Racusin initially thought something was wrong. Within minutes, however, as reports from other observers arrived, it was clear this was a special
event.

Gamma-ray bursts are the universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As a star's core collapses, it creates a black hole or neutron star that, through processes not fully understood, drive powerful gas jets outward. These jets punch through the collapsing star. As the jets shoot into space, they strike gas previously shed by the star and heat it. That generates bright afterglows.

The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 of a degree across. This core resided within a slightly less energetic jet about 20 times wider. "It's this wide jet that Swift usually sees from other bursts," Racusin explained. "Maybe every gamma-ray burst contains a narrow jet, too, but astronomers miss them because we don't see them head-on." Such an alignment occurs by chance only about once a decade, so a GRB 080319B is a rare catch.

Swift is managed by Goddard. It was built and is being operated in collaboration with Penn State, the Los Alamos National Laboratory, and General Dynamics in the U.S.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus additional partners in Germany and Japan.

Mercury fly-by benefits

MESSENGER flew past the planet Mercury a few weeks ago with all its instruments gathering a wealth of data.

The preliminary science results were presented at a press conference on Jan 30, and those results are summarized well in the Planetary Society's blog.

As the author of that blog noted, however, there was another outcome in the press conference.

One of the press questions at the end was from a tiny local radio station who said that he knew he was being listened to by an audience of schoolkids; what would the science panel say to those kids? One panelist, Bob Strom, talked briefly about how much of a "turn-on" science was, which was a bit awkward; but, with a couple more minutes to think, Sean Solomon [the MESSENGER PI] really stepped up. Here's what he said:

Space exploration is a lot more than space science. We're flying a spacecraft that owes its origin and livelihood to hundreds of engineers and technicians who designed it, who worried about how it would survive so close to the Sun, how it would survive radiation, how it would live for nearly 8 years, how it would communicate its scientific findings back to the Earth, how it would get launched, how it would find its way billions of miles, 15 times around the Sun, to get into Mercury orbit 6 and a half years following its launch. There are a lot of ways to contribute to space exploration. Science is one of them. The engineering of building, operating, and maintaining spacecraft is a terrific field, and we [gesturing to the panel] would not be up here if we did not have an outstanding team of engineers who put this spacecraft together and keep it going.

I couldn't say it better myself!

September Aurora

There's a pretty good possibility of nights with Aurora Borealis in the next two weeks.

The Sun's rotation is bringing a very active sunspot area back into view. Yesterday that area, barely visible, coughed up a solar flare which caused a complete blackout of shortwave radio communication over the daylight side of the Earth -- impressive for a glancing blow. As the Sun brings that area round to face the Earth, things could get even more violent.

This was an "X-Class" flare: "X-class flares are big; they are major events that can trigger planet-wide radio blackouts and long-lasting radiation storms." Their strength is measured on a scale of 1 to 9 (X-1 to X-9) -- yesterday's was an X-17. If another one of those explodes when that active region is central on the Sun (pointing at, or near, the Earth) in about a week's time, we should have quite a show! As some of us saw, the Moon was very new on Monday, so it'll be full and bright in about ten days and may spoil any show.

The all-time record is a flare in November 2003 which overloaded every X-ray detector on the satellites which monitor this stuff - it's estimated to have been in the X-30 to X-40 range, beating the previous record of about X-24. Luckily the material blown off the Sun by that one missed the earth. In March 1989 a X-15 solar storm took out the Quebec region's electrical power grid.

If anything happens SpaceWeather will have news ....