[meteorite-list] New Horizons: Nine Years to the Ninth Planet, and Counting

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Jul 14 12:08:28 2006
Message-ID: <200607141510.IAA04248_at_zagami.jpl.nasa.gov>

http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_current.php

The PI's Perspective
Nine Years to the Ninth Planet, and Counting
Alan Stern
July 14, 2006

Today, July 14, we stand precisely nine years from our closest approach
date with the ninth planet and her moons. Next week, on July 19, we will
celebrate the six-month anniversary of our launch. New Horizons has a
long way to go, but we're on our way!

It's been six weeks since my last column here, and a lot has taken
place. Here's a short list of highlights:

    * New Horizons successfully conducted an asteroid flyby test of its
      moving target image motion compensation system (more on that below).
    * The names we nominated for Pluto's two recently discovered small
      moons, Nix (the inner one) and Hydra (the outer one), were
      approved by the International Astronomical Union (IAU).
    * Continued successful testing of the SWAP and PEPSSI plasma/high
      energy particle detector suite aboard New Horizons.
    * Successful beam mapping tests of the REX-High Gain Antenna pattern.
    * Uploading of an updated (yes, "new and improved") release of the
      onboard fault detection and correction "autonomy" software that
      watches over New Horizons.
    * A spin-up maneuver that took New Horizons out of three-axis
      attitude control and placed it back in its 5 RPM axial spin to
      save fuel and place us in a more robust mode for the upcoming
      flight software loads of August and September.

Traveling more than 70,000 kilometers (43,500 miles) per hour, 24x7, New
Horizons is now closer to Jupiter than it is to the Sun; check this out
at http://www.pluto.jhuapl.edu/mission/whereis_nh.php. By the end of
July our ship will be passing the distance of Ceres, the largest member
of the asteroid belt and a relic of our solar system's planetary
formation days.

Ceres and Pluto have something important in common: They are both dwarf
planets. Ceres is about twice as small and twice as dense as Pluto, the
latter because it formed about 10 times closer to the Sun. With the
discovery of other dwarf planets in the Kuiper Belt it has become clear
that the solar system we once thought of as consisting of four
terrestrial planets, four giant planets, and a misfit planet named Pluto
isn't that at all. In fact, the solar system appears to contain at least
dozens of dwarf planets - perhaps more - quantitative population
estimates as high as 1,000 dwarfs can be found in the technical literature.

No dwarf planet has - as yet - ever been visited by a spacecraft, but in
2015 that will change dramatically. If all goes well, not only will New
Horizons fly by Pluto, but NASA's mission
will visit and go into orbit about Ceres as well that year. Together
these two missions will revolutionize our knowledge of the dwarf worlds
that dominate the planetary census of our solar system. And I'll wager
that in the wake of these two explorations, calls for new missions to
further investigate the exotic and diverse dwarf planet population of
the solar system will be made - after all, the dwarfs hold a wealth of
information on the mid-stage of the planet building process.

Now I want to briefly recap the encounter of New Horizons with asteroid
2002 JF56, something I wrote about with some anticipation last month, as
the planning for this event was taking place. Because the opportunity to
fly by this small asteroid came up only in May, our mission and payload
operations planning teams had to swing quickly into action. It took long
hours of work, but they planned and executed this encounter in just six
weeks. On June 11 and 13, observations of 2002 JF56 were made with the
Ralph MVIC color camera, MVIC's panchromatic cameras, and Ralph's LEISA
infrared imaging spectrometer.

<image>
Ralph MVIC imagery of asteroid 2002 JF56 made on June 13, 2006, as New
Horizons flew by it at a relative speed of over 70,000 km/hour. As hoped
for, the moving asteroid was sharply resolved and stars were smeared as
the spacecraft tracked on the position of the moving asteroid.

Because we flew far from "JF56" - just over 102,000 kilometers (65,000 miles) -
we weren't able to return the kind of spectacular images that dedicated
asteroid missions do. But we nonetheless measured the color, photometric
properties, size, and composition of JF56. And most importantly, as
noted above, we proved we could correctly "point and shoot" at moving
targets. The composite of image snippets below shows this, revealing
Ralph MVIC images of both JF56 and nearby stars. As you can see, the
stars were streaked but JF56 was as steady as we could ever have hoped
for. This gives us the warm glow of direct experience to build
confidence in our tracking of moving targets for the New Horizons flybys
of Jupiter next year, Pluto in 2015, and the Kuiper Belt thereafter.

Owing to the great success of this flyby test, I've nominated the name
"Johns Hopkins Applied Physics Lab" to the International Astronomical
Union for 2002 JF56. Caltech's Jet Propulsion Lab has had an asteroid
named after it for some years now, and I really can't think of a better
moniker for the New Horizons target than one that honors the APL team
who made New Horizons happen. Go New Horizons, Go APL!

Before closing out this column, I also want to report that a team of
astronomers successfully captured an occultation of a star by Pluto last
month, on June 12. These kinds of events are rare but valuable. They are
rare because Pluto's size is so small (just under 0.1 arcseconds, or
1/40,000 of a degree in diameter) that it rarely gets in front of a star
of useable brightness. Occultation events are valuable primarily because
they allow us to probe the structure of Pluto's atmosphere. It takes
painstaking work just to accurately predict the occurrence of such
events, and even more work to stage expeditionary teams to observatories
and even more remote sites with portable telescopes.

The June 12 occultation effort was led by Dr. Leslie Young, the New
Horizons deputy project scientist and an expert in the study of
planetary atmospheres. Other New Horizons team members like Drs. Cathy
Olkin and Eliot Young participated in both the planning and observing at
various locales. This particular event was best observed in Australia
and New Zealand, where Pluto's shadow passed over the Earth. Best
positioned there was Dr. Richard G. French of Wellesley College, an
occultation studies expert, who was at the 3.6-meter diameter
Anglo-Australian Telescope near Coonabarabran, New South Wales (see
http://www.coonabarabran.com/ and
http://www.daviddarling.info/encyclopedia/A/AAT.html ).

The data retrieved by Dr. French and others in Australia and New Zealand
on June 12 show that Pluto's atmosphere today is a lot like it was at
the time of two occultation events in 2002, but fairly different than in
1980s occultation events. Most specifically, Pluto's lower atmosphere
seems to have undergone some kind of change in its haze content or
thermal properties since the 1980s, when it passed perihelion (closest
approach to the Sun).

We'll have to wait a few months for data analysis to yield quantitative
results, but I can say without reservation that Pluto's atmosphere
"hasn't collapsed yet" (though there can be no guarantees about what
will happen before we arrive in 2015). Meanwhile, New Horizons races
Plutoward, to assay its atmosphere in exquisite detail.

I'll close with one last tidbit. The New Horizons Jupiter Encounter
Science Team (yes, JEST), led by Dr. Jeff Moore of NASA Ames and Dr.
John Spencer of Southwest Research Institute, has turned in its Jupiter
observation plan. This plan was formally communicated to the mission
operations team in an all-day review on June 26. The Jupiter observing
plan, which stretches from January to June 2007, has more than 500
separate observations in it. Observations resulting from this plan
should yield major advances on everything in the Jupiter system from the
Galilean satellites to the red spots to Jupiter's magnetosphere and
aurora, and the Jovian rings.

Now it's up to the mission planners to make this plan a reality. There's
no doubt it'll be a challenge to plan for and execute hundreds of
separate observations, but the mission ops team has signed up to give it
their all, and I know they'll do a fantastic job sequencing as much as
possible over the next few months.

Well, that's all I have for now. Until next time, keep exploring!
Received on Fri 14 Jul 2006 11:10:51 AM PDT