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New Horizons Hibernation and Cruise to Pluto
edstrick
post Sep 19 2007, 08:18 AM
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I would expect so.
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Alan Stern
post Nov 20 2007, 09:27 AM
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UMSFers-- To Be Posted at the NH mission website today, with illustrations:



The PI’s Perspective
November 19, 2007

Autumn, 2007: Onward To the Kuiper Belt

New Horizons rolls out to launch on January 16, 2006. The trees in the foreground reveal the vehicle’s true size.

New Horizons has now covered 85% of the distance from the Sun to Saturn’s orbit, which it will pass in mid-2008. Of course, Saturn will be nowhere near New Horizons when we pass that milestone, as it is by chance located far around the Sun from the path New Horizons is following to Pluto, but as you can tell, we are really getting to be well into the outer solar system now

Since I last wrote you, at the start of October, the New Horizons team has been busy on two major fronts. One of these has been planning and executing our 2007 “Annual Checkout” (ACO) of the spacecraft and its payload. As our first ACO, this three-month operation has been a pathfinder for the team, teaching us how to make improvements for subsequent ACOs in 2008, 2009 and beyond.

The other front we’ve been working on is Pluto encounter planning. As I’ve written here before, we are planning for Pluto now, to take advantage of the experienced team that took us through our virtually flawless Jupiter encounter earlier this year. Budget constraints will force us to slim down the team in mid-2009, so we need to finish the Pluto planning before many of the Jupiter encounter team members move on to other projects.

Our first Annual Checkout was a great success. In fact, ACO-1 just wrapped up, after more than 500 separate spacecraft and instrument activities. We also took the data to recalibrate our instruments — something we’ll do several times as we fly out to the Pluto system. As you know from my last posting here, we also planned and successfully accomplished an engine burn during ACO-1. This maneuver refined our course and dramatically narrowed our expected trajectory errors at Pluto.

We did have a couple of unexpected events in ACO-1. One came in early October when the spacecraft partially lost track of its timeline owing to a very subtle kind of error generated by a command script we’d sent it. The operations team caught this and recovered from it very quickly. It’s was really a blessing that this subtle behavioral flaw manifested itself now, rather than at Pluto, so we can protect against it. It’s just these kinds of idiosyncrasies that our testing and flight operations hope to expose, so despite the fact it cost us some lost sleep and some cruise science observations, we’re very glad to have learned this lesson.

The second unexpected event came just last week, on November 12th, when a cosmic ray or some other kind of charged particle caused our main computer to reboot. This is the fourth such computer reboot we have had in flight owing to space radiation bursts. Preflight predictions were for these events to be far rarer than this, and our engineering team is looking into why this is occurring more often than predicted. Fortunately, on all four occasions this occurred, the onboard spacecraft autonomy software performed as planned and recovered New Horizons safely.

The third and final such event took place on November 16th when the spacecraft main computer executed a power on reset (POR) due to a glitch on its power line. Because this was so unexpected, we are currently analyzing what happened and have decided not to enter hibernation until late December while we analyze the root cause of this anomaly and put in place some software protection against future events. For the next couple of weeks, we’ll monitor the spacecraft three to four times per week using NASA’s Deep Space Network to collect more data.

Then, between December 11 and 17, the spacecraft will pass near the Sun as seen from Earth. (Don’t worry, New Horizons really is out in the frigid cold near Saturn, it just appears to be near the Sun when seen from Earth’s vantage point.) This event is called “solar conjunction” and it occurs every year as the Earth itself reaches a point nearly opposite the Sun from New Horizons. As during last year’s solar conjunction, we will lose contact with New Horizons due to radio interference from the Sun, which will be just one to three degrees away from New Horizons and in our tracking antennas’ field of view.

December 17, the day we exit this year’s solar conjunction, is an anniversary for us, as on that day in 2005, New Horizons was lifted onto its Atlas launch vehicle down in Florida. It’s a nice coincidence to note that precisely 102 years before that day, in 1903, the Wright brothers made their first flight at Kitty Hawk.

And as we exit solar conjunction on December 17th, we’ll have a fairly intense week of activity. During that week we will re-point our dish antenna to better position it for communications with Earth, play back recorded engineering and Student Dust Counter detector telemetry; and prepare the spacecraft for a long period of hibernation that will begin on December 23 and continue uninterrupted (we hope!) until next May when we next break hibernation for about a week to reposition our antenna again for better communications with Earth. We’ll also use that operations opportunity in May to send home some of the lower priority “cruise science” data taken this month that couldn’t be squeezed down during ACO-1. And then we’ll go back to silent running until ACO-2 begins late next September.

During the almost 40 weeks we’ll be in hibernation in 2008, we won’t be sending commands to the spacecraft, but we will check its health via weekly beacon tones and (beginning in early 2008) monthly telemetry sessions. Many of you may notice that this is a less frequent set of checks than we performed in 2007– because as we gain experience with the spacecraft in hibernation mode, we can reduce the oversight we perform on it. This “lengthening of the leash” as I like to call it, is something we have planned for years. And unless something untoward occurs, this pace of weekly beacon tone and monthly telemetry checks is how we will run hibernation activities in future years on the way to Pluto.

That’s my update on mission activities for now, but before I close I’d like to show you two things related to the Pluto encounter we are now beginning to plan.

First is the “block schedule” that defines our Pluto system encounter phases. By studying this figure–which I’ve placed below--you will see that we plan to begin the encounter operations about 6 months before reaching Pluto, and we do not finish—including all of the data transmissions and plasma and dust environment measurements until 6 months after the July 14 encounter itself. Of course, most of the action occurs in the roughly two-month period centered on encounter day, when our resolution and sensitivity are dramatically better than anything Earth-based and Earth-orbiting telescopes can match.

New Horizons’ encounter with the Pluto system will span a year, in which there will be three successively closer approach phases (APs 1, 2 and 3), a near encounter phase (NEP) lasting two days, which will be followed by three successively more distant departure phases (DPs 1, 2 and 3).

The second encounter-related diagram I want to show you is a view of the Pluto system at our moment of closest approach. It shows where the spacecraft will be at its moment of closest approach to Pluto, relative to Pluto and all three of Pluto’s satellites, i.e., at the green “+” symbol. As you can see, we will be 13,700 kilometers from Pluto’s center and therefore 12,500 kilometers from its surface. You can also see that Nix and Charon are arrayed on different sides of the spacecraft at roughly similar distances, but Hydra is considerably farther away, off in the rough direction that Charon will appear to be.

The geometry of Pluto and its three satellites – Charon, Nix and Hydra – are shown here relative to our spacecraft aim point (the green “+”) at the moment of closest approach (C/A) to Pluto.

In the coming year while our beauty sleeps, we will plan this encounter in great detail, leading to a full suite of rehearsals on our mission simulator in 2009, which will in turn lead to rehearsals on New Horizons itself in 2010. As 2008 unfolds, I’ll keep you apprised of many of the interesting things we plan to do during the Pluto encounter and how we plan to do them.

Well, that catches you up with where New Horizons is and what the spacecraft and project team have been doing. I’ll be back with more news around the start of the new year. In the meantime, keep on exploring, just like we do!

-Alan Stern
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djellison
post Nov 20 2007, 09:44 AM
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When do you sleep!! Thanks, as ever, for the update - much appreciated.
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Alan Stern
post Nov 20 2007, 09:53 AM
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QUOTE (djellison @ Nov 20 2007, 09:44 AM) *
When do you sleep!! Thanks, as ever, for the update - much appreciated.


And you Doug?
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ugordan
post Nov 20 2007, 10:43 AM
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Thanks for the heads up, Alan. As always, one notices the bad news first:

QUOTE (Alan Stern @ Nov 20 2007, 10:27 AM) *
The second unexpected event came just last week, on November 12th, when a cosmic ray or some other kind of charged particle caused our main computer to reboot. This is the fourth such computer reboot we have had in flight owing to space radiation bursts. Preflight predictions were for these events to be far rarer than this, and our engineering team is looking into why this is occurring more often than predicted. Fortunately, on all four occasions this occurred, the onboard spacecraft autonomy software performed as planned and recovered New Horizons safely.

Is this a concern for Pluto approach observations, e.g. are you expecting to be able to deliver a software udate which would recognize these kinds of events and would not result in a safing event which terminates the observation sequence? I'm thinking of something similar to what was recently incorporated into Cassini flight s/w. Recalling the recent Iapetus flyby and the safing event, it would be tragic to have something similar occur during Pluto C/A.


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djellison
post Nov 20 2007, 10:49 AM
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I'm a Brit, so I'm 5hrs ahead. Infact, I feel a cup of tea coming on.

I'm reminded of something from 'The Last Lecture of Randy Pausch' - he said people ask him what his secret is to being so succesfull - his reply 'Call me in my office any Friday night at 10 O'clock and I'll tell you'


Doug
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nprev
post Nov 20 2007, 11:51 AM
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Well, I'm selfishly thankful for the fact that BOTH of you guys are insomniacs (me too, but much, much less productive); awesome update, Alan, thank you! smile.gif

Kind of curious about the energetic particle situation. IIRC, the terrestrial observatories looking for 'shower' events is just coming online, so there isn't a very good baseline yet to evaluate the overall environment in this regard. Do you suppose that it's been heavier than average of late, given that Cassini also experienced an event not too long ago? Don't know if other missions have had any problems.


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ElkGroveDan
post Nov 20 2007, 03:56 PM
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QUOTE (Alan Stern @ Nov 20 2007, 01:27 AM) *
New Horizons has now covered 85% of the distance from the Sun to Saturn’s orbit, which it will pass in mid-2008.


Holy smokes! These kinds of velocities are just mind blowing.

Thanks again for dropping by here for us Alan.


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If Occam had heard my theory, things would be very different now.
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jasedm
post Nov 20 2007, 09:52 PM
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Thank you very much for the information - great to have some idea of the situation around C/A - I can only begin to imagine the flurry of activity and sleepless nights/overtime when, a couple of weeks prior, 3 or 4 more moons turn up on the approach imagery and some rings/ring arcs hove into view.......
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mchan
post Nov 21 2007, 05:45 AM
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QUOTE (nprev @ Nov 20 2007, 03:51 AM) *
IIRC, the terrestrial observatories looking for 'shower' events is just coming online, so there isn't a very good baseline yet to evaluate the overall environment in this regard. Do you suppose that it's been heavier than average of late, given that Cassini also experienced an event not too long ago?


Neutron monitors have been around since around the time Sputnik-1 launched. These detect secondary particles created by collisions with atmosphere molecules. The intensity is that on Earth's surface and it varies with the 11 year solar cycle. The data does not reflect (at least not directly) what is experienced by spacecraft in deep space.

Space Physics Data System has many links to historical data in many formats. One of the links is to a monitor in Moscow with real time data. Have fun.
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nprev
post Nov 21 2007, 10:15 AM
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What a terrific resource; thanks very much, mchan! smile.gif Gotta go play with it now...

EDIT: It sort of looks like CR activity was pretty busy on 11-12 Nov, but it actually looks busier 19-20 Nov. It's all a roll of the dice, anyhow; since these things are thought to be the result of random high-energy astrophysical events (and, apparently, Centaurus A's central black hole & those of other active galaxies burping every so often as they eat), there's no way to predict them.


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Alan Stern
post Nov 21 2007, 11:36 AM
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QUOTE (ugordan @ Nov 20 2007, 10:43 AM) *
Thanks for the heads up, Alan. As always, one notices the bad news first:
Is this a concern for Pluto approach observations, e.g. are you expecting to be able to deliver a software udate which would recognize these kinds of events and would not result in a safing event which terminates the observation sequence? I'm thinking of something similar to what was recently incorporated into Cassini flight s/w. Recalling the recent Iapetus flyby and the safing event, it would be tragic to have something similar occur during Pluto C/A.


Ugordan- Actually, during encounter we plan to lock out most of the autonomy that would safe the s/c. The logic here is that we have only one shot at encounter and you want to ride out events like reboots rather than calling home for help which can only come after the main festivities would be over. By contrast, in cruise, one always has time to ring home and play it safe...

-Alan
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Guest_PhilCo126_*
post Nov 21 2007, 06:11 PM
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After a 35 years long experience of venturing out past the outer planets (since Pioneer 10: Jupiter Dec 1973 - Neptune June 1983) I guess we can sleep on both ears concerning the radiation-hardened computer unsure.gif
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Liss
post Feb 26 2008, 08:18 AM
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I'm somewhat at loss regarding the current status of New Horizons.
Was it put to hibernation on February 21 as scheduled?
Was it put to hibernation earlier on December 23 as advertised? If not, why? Else, what was the reason to wake up her between December and February and when was it done?
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