New Horizons, Pluto and the Kuiper belt Options

[edstrick]

Bob Shaw: "..you *can* visit the Sun, you just have to go at night when it's cooled down!)...."

It takes an awful lot of billions of years for a white dwarf to cool down enough to land on, once the sun has finished fusion and died.

[Bob Shaw]

Bob Shaw: "..you *can* visit the Sun, you just have to go at night when it's cooled down!)...."

It takes an awful lot of billions of years for a white dwarf to cool down enough to land on, once the sun has finished fusion and died.

Hey, no problem - it'll happen just after the VSE is completed and the ISS is finished!

Bob Shaw

[Alan Stern]

For those interested, the Ralph turn on this past week went well, all modes were operated, including
pan and color imaging, and LEISA, but we were spinning and the front (aperture) door was closed so
we do not consider this first light.

This cming week SWAP gets to HV testing and therefore the particle equivalent of "first light."
Mid-week we will re-boot the main computers with new C&DH software, load 3.5, which has some
risk-reducing bug fixes.

Meanwhile, here on Earth, we're negotiating budgets with NASA for the flight mission and moving
to our last planning review of Jupiter encounter science goals and observations lists.

[MahFL]

Thanks for the update, we are always interested

Michael, FL.

[mchan]

A new PI update is posted on the NH website that talks about aforementioned SW load as well as status of instrument calibrations.

http://pluto.jhuapl.edu/

[Alan Stern]

For the cognoscenti, here's an advance copy of the PI Update about to appear at pluto.jhuapl.edu, enjoy!

New Horizons has entered the asteroid belt and will be traversing this part of our solar system through August. The schematic view above shows the scale of the asteroid belt compared to the orbits of the Earth, Mars, and Jupiter, each shown in blue. The sizes of the asteroids in this illustration are vastly exaggerated—the belt is in reality almost entirely open space. The “Trojan” asteroids orbiting ahead and behind Jupiter are a different dynamical class of small bodies in our solar system.

May, like April, was a busy month for New Horizons instrument payload commissioning. In particular, our instruments LORRI, PEPSSI, Alice, and Ralph all continued their in-flight checkouts. In addition, the spacecraft itself received a new suite of onboard fault protection autonomy software resolving a number of bug fixes discovered in ground and flight testing. We continue to see software-induced guidance computer resets once or twice per month on average, but the spacecraft recovers flawlessly from these, without any interruption to plans. New software for this computer is in work that will resolve the bug that causes this; we expect to have that load tested and aboard the spacecraft around October 1st.

Highlights of our payload commissioning activities included door openings for PEPSSI (May 3rd), Alice (May 20th), and Ralph (May 29th). The Student Dust Counter (SDC) registered each of these events at the precise time of the door openings by the noise they made on the spacecraft Each of these instruments also saw “first light,” i.e., detecting signals from stars (Ralph) or the interplanetary medium (PEPSSI and Alice). From these test we appear to have a little higher than spec sensitivity with Ralph’s color and panchromatic cameras. Also, Alice’s background counts are only about half what we predicted, indicating that the RTG induces a significantly lower background than we estimated before launch. This lower background rate will significantly enhance Alice’s signal to noise ratio on faint spectral features.

From the Alice, Ralph, and PEPSSI testing this month we can continue to say that from all of the data surrounding the careful, step-by-step instrument commissioning activities to date, our instrument payload continues to look like its performing as well or better than predicted from ground testing. This is a testament to the exacting engineering that went into their development.

In other news for May, we began to finalize the suite of Jupiter observations planned for next year during our Jupiter flyby, and we continued to track New Horizons to determine whether a fine course correction will be needed this fall. So far, no course correction appears necessary, but the final verdict won’t be in until we have about another 90 to 100 days of tracking.

Planning activities began in May for the annual, 60 day checkouts we’ll perform each year each year during Cruise 2 (“Glen’s Glide”)—the coast from Jupiter to Pluto. From 2008 to 2011 these checkouts will occur in the fall of each year. But in 2012, 2013, and 2014, our annual checkouts will occur in the summer. Summertime checkouts will occur in 2012 and 2014 because we’ll be rehearsing the Pluto encounter aboard the spacecraft, and we want the Earth-Sun geometry at rehearsal time to faithfully reproduce what will occur at encounter—in the summer of 2015.

I’ll now turn to the “water cooler news story” of the month for New Horizons: In early May, we also got word from Lockheed-Martin that tourists in the Bahamas found several large pieces of our Atlas V 551 launch vehicle’s nose fairing that washed up on shore.

Now let’s talk about the significance of our current location: deep in the solar system’s asteroid belt. As both the title and the first illustration in this month’s blog indicate, we’re traversing the main asteroid belt now. This region of the solar system consists of a handful of dwarf planets, like Ceres (itself 1000 kilometers in diameter), and literally millions of debris bits created by collisions between asteroids. These small bodies range up in size from mountains to objects as large as 100 kilometers across. The asteroid belt also contains innumerable boulders, rocks, and dust motes created by the same collisions. There are many good web sites describing what is known about the asteroid belt. One I hope you’ll like can be found at: http://www.solstation.com/stars/asteroid.htm; another good site is at http://en.wikipedia.org/wiki/Asteroid_belt.

The first spacecraft to transit the asteroid belt was NASA’s Pioneer 10, which made its epic crossing in 1972 on the way to the historic first encounter of a spacecraft with Jupiter. Later, Pioneer 11, Voyagers 1 and 2, Galileo, Cassini, NEAR, and Ulysses have all made the same kind of journey across the main belt. Now it is our turn. Fortunately, the asteroid belt is so huge that, despite its large population of small bodies, the chance of running into one is almost vanishingly small—far less than one in one billion. That means that if you want to actually come close enough to an asteroid to make detailed studies of it, you have to aim for a specific asteroid.

The first such asteroid flyby was made by Galileo in October, 1991. Galileo also made a second asteroid encounter in 1994. Other spacecraft, most notably the NEAR (Near Earth Asteroid Rendezvous) mission have also made close main belt asteroid flybys, yielding important geological and geophysical insights into these bodies. Galileo also made the first discovery of an asteroid satellite in it’s 1991 of asteroid Gaspra—since then, groundbased observers have found dozens of asteroid satellites. In addition to main belt asteroid flybys, NASA’s NEAR and the Japanese Hayabusa mission have both made orbital rendezvous and landings on asteroids closer to Earth. And next year, NASA plans to launch the Dawn (http://dawn.jpl.nasa.gov/) Discovery mission to orbit two of the largest asteroids—Vest and Ceres. Dawn will arrive in orbit about Vesta in 2012, and will reach Ceres, the largest asteroid, in August 2015, just a month or so after New Horizons encounters Pluto.

A long time ago, we considered the possibility of targeting a close asteroid flyby with New Horizons during our crossing of the main belt. As the mission PI, I rejected this early on for two reasons. First, such an encounter would take about half of our Kuiper Belt fuel to accomplish. Secondly, even for this amount of fuel, the only asteroids we could hope to reach would be tiny—just a few kilometers across. While such an encounter would certainly be scientifically useful, it couldn’t be justified for the amount of Kuiper Belt fuel it would cost us. And when all is said and done, after all, our job is to reconnoiter bodies in the Kuiper belt.

Although we specifically decided not to target any asteroid, after launch we did conduct a thorough search for chance encounters along our trajectory. Just the statistics of such chance encounters indicated that we might expect to pass perhaps 1 to 3 million kilometers from a small asteroid by chance as we transited the main belt. We found several such opportunities back in February.

But as it turns out, we got more than what we expected: in early May we also discovered that we’d pass within just 104,000 kilometers of the little known asteroid 2002 JF56 on 13 June! This little mountain-sized body (http://smass.mit.edu/2002jf56.html) is only 3 to 5 kilometers across; and virtually nothing is known about it—not even its compositional type or its rotational period.

Although we cannot resolve something as small as 2002 JF56 from this distance with Ralph (LORRI, which has higher resolution cannot open its door until late August to guard against accidental Sun pointings), the 13 June “encounter” with 2002 JF56 is still going to be useful to New Horizons.

The primary use of this distant flyby will be to test Ralph’s optical navigation and moving target tracking capabilities. We will also be able to get a handle on the asteroid’s lightcurve, composition, phase curve, and perhaps even refine its diameter if all goes as planned. But this event is really a flight test, so we aren’t guaranteeing anything but a best effort. If it works, you’ll see images that just barely resolve the asteroid into perhaps 1 or 2 pixels and perhaps a spectrum of this chip off some larger body. More importantly, of course, we will gain some valuable experience that will yield benefits at both the Jupiter and Pluto flybys, so we’re excited to give this a try.

Stay tuned, we’ll report on the results at mid-month on this web site.

On June 13th, New Horizons will pass just 104,000 kilometers from a small main belt asteroid called 2002 JF56. This fortuitous encounter is too far away for detailed imagery, but it will allow us moving target tracking capabilities. The positions of 2002 JF56 and New Horizons are illustrated here for June 1st.

Flight activities for June will center on SWAP instrument testing, Ralph instrument calibrations, and beam mapping observations for our high gain antenna and REX (radio science) instrument. By July 4th, we’ll be 3 AU from the Sun. Although the sunlight there is still 100 times as strong as it is on the brightest day at Pluto, it’ll be about ten times dimmer than at Earth’s orbit. Less than 6 months into a 114 month journey to Pluto, New Horizons is beginning to reach the cooler thermal conditions it was designed to thrive in!

OK, that's it for now. So until next time, keep exploring.

-Alan Stern

[hendric]

Great news about the encounter Alan! It's too bad LORRI can't take a peek, but I understand 100% why, especially with the guidance computer taking resets like that. Any news on that potential Centaur or Neptune Trojans?

[RNeuhaus]

Alan, very entertaining report along with a brief tourist space guidance: There are
Jupiter Trojans asteroides, on the left hand are Martian Trojans, and on the right hand are one of many NEO.

Rodolfo

[mchan]

Alan, thanks for the preview. As usual, it is informative and gives a sense of involvement to us armchair folks.

[Alan Stern]

Great news about the encounter Alan! It's too bad LORRI can't take a peek, but I understand 100% why, especially with the guidance computer taking resets like that. Any news on that potential Centaur or Neptune Trojans?

Hendric-- No news. I expect the Centaur search to evolve slowly, over years. Ditto the Trojans.
The odds are low that we'll get anything good: perhaps 10%. But my concience tells me 10% is high
enough to have a good look and see. It would not be worth the effort had it been a 1% chance.

-Alan

[hendric]

Just re-found Petr's excellent asteroid group webpage, with animations of various groups. The Jupiter Trojans with the Hilda group is very nice.

http://sajri.astronomy.cz/asteroidgroups/groups.htm

Also, it appears there are now 4 Neptune trojans, but they're on the wrong side of Neptune!

http://www.cfa.harvard.edu/iau/lists/Trojans.html

Looks like they could potentially be 30-150 km in size, based on absolute magnitude.

Just curious, it looks like Neptune would have lost many of its Trojans (75%) during its migration inwards:

http://arxiv.org/pdf/astro-ph/0305572

[Rob Pinnegar]

Regarding the four known Neptune Trojans all being on the "wrong side" of Neptune:

Pluto is in Sagittarius at the moment, so the Trojan region that is on the "right side" of Neptune shouldn't be too far away from it. This is probably one of the reasons no targetable Trojans have been found yet... any of the Neptunian Trojans we might be interested in could very well be lost in the Milky Way.

In other news, Pluto is going to occult a 15th magnitude star on June 12th... and P2 may also occult the star, as seen from positions in Australia. For the details check:

http://www.iota-es.de/pluto384.html

[dilo]

Just re-found Petr's excellent asteroid group webpage, with animations of various groups. The Jupiter Trojans with the Hilda group is very nice.

This site is really great, with fabulous plots and animations! Thanks hendric.

[RNeuhaus]

More details about Pluto New Horizons Mission Supporting Observations for 2002 JF56 (3-5 km of size). Encounter Date 13 June 2006 UT at about 100,000 km

http://smass.mit.edu/2002jf56.html

Possible photometric and spectroscopic measurements obtained by the spacecraft will be most useful if supported by ground-based observations.

Rodolfo

[climber]

Thanks so much Alan. It's so different to get a status from You on UMSF than to read it on NH website or JPL's. Even if words could be the same (and they aren't this time) we feel like to be more "involved" in the mission and I guess that this is the dream of most of us.