Weather on Pluto. Fair, haze patches at first. Moderate calm with the occasional chop.

The July 23, 2013 morning session of the Pluto Science Conference started with a collection of talks addressing what we know and what we don’t know about Pluto’s atmosphere.

Emmanuel Lellouch (Paris Observatory, France) spoke about “Pluto’s Atmosphere: Current Knowledge and Open Questions.”

What do we know about Pluto’s Atmosphere? We know that it is a nitrogen (N2) dominated atmosphere with methane (CH4) (tens of %) and probably carbon monoxide (CO). It’s about 10-microbar (pressure) class showing evidence for changes in pressure on year/decade timescales. There is also evidence for waves (dynamic changes), and the atmosphere does have a thermal structure, despite the details being hotly debated in the community (pun intended). People do agree that the surface is cold (40-50 K) and then the atmosphere is around 100K at micro-bar pressure levels. The details of the cold/warm layers in between are the stuff that thermal models are made of!

Pluto was discovered in 1930, but it was only in 1985 that the first observation detecting an atmosphere around Pluto was made. It was discovered through a measurement called a stellar occultation, when Pluto crossed between a star and an observer on Earth, on August 19, 1985 (Brosch, MNRAS, 1995). A higher signal-to-noise light curve was obtained on the June 9, 1988 (Elliot, et al 1989) occultation events whose light curves indicated existence of waves.

Occultation light curve for Pluto passing in front of a star on Jun 9, 1988

Occultation light curve for Pluto passing in front of a star on June 9, 1988 (signal vs. time) Features in this dataset indicate the upper atmosphere (above the ‘kink’) and lower atmosphere (below the ‘kink’). The ‘kink’ presence is theorized to be due to heating by methane (Hubbard et al 1990). Waves are indicated by the “spikes” in the light curve. When the scientists create this light curve from the occultation event, they then “invert” it to fit a temperature model and derive pressures for different scale heights.

The first molecular detection of anything in the Pluto’s atmosphere was methane (L. Young et al 1997) using the IRTF (3.5 m telescope) in May 1992. This was confirmed and re-measured in 2008 with higher resolutions and sensitivity (Lellouch et al 2009) using the VLT (8 meter telescope) with more recent observations in 2012. Emmanuel Lellouch showed that with those two latter datasets there was no evidence of change in the last four years. With this higher resolution data they can use it to provide a fit to the temperature using the line widths.

Carbon monoxide (CO) was detected in the submillimeter at 240 GHz with JCMT (Greaves et al 2011), but this detection and the inferred amount has lead to questions that the current models cannot produce this molecule with the temperature and amount inferred from the observations. This particular topic was addressed by Mark Gurwell’s talk later in the morning.

There is also evidence for diluted methane (CH4) and pure CH4 ice on Pluto’s surface. The atmosphere CH4 is much greater than what is expected from an ideal mixture, so this implies there must be a mechanism to enrich the CH4 component in Pluto’s atmosphere. Recent thermo-dynamic models and “GCMs” (general circulation models) predict a consistent mixture for CH4.

The combination of both the infrared spectral results and the visible (and in some case near-infrared) occultation light profiles helps resolve temperature profile (i.e., how temperature varies with altitude) inconsistences.

Speaking of temperature profiles, one of the hotly debated topics for Pluto atmosphere specialists is whether their models contain a tropopause. Per Emmanuel Lellouch’s overview talk, he stated, “There is no proof there is a troposphere. And deep troposphere are not predicted by the GCMs.” However, many Pluto atmosphere specialists often invoke a troposphere in their calculations to help predict other things that have been inferred to occur on Pluto.

Pluto’s atmosphere seems to be changing. There is observation of pressure evolution. Specifically, the pressure appears to have doubled from 1988 to 2002 (Sicardy et al 2003, Eliot et al 2003). Evidence that the pressure is continuing to increase is based on recent 2013 occultation data. This has led to the development of Volatile Transport Models. These are basically computations that track the dominant species, and for Pluto, it is nitrogen, through multiple temperature and pressure ranges, heat exchanges such as sublimation cooling in summer and condensation heating in winter. A schematic of a Volatile Transport Model from Leslie Young, New Horizons deputy Project Scientist, is shown below.

Schematic of a volatile transport model for Pluto

Schematic of a volatile transport model for Pluto. More details about the model are in a blog on Leslie Young’s volatile transport model talk later in the conference.

Other Oddities in Pluto’s Atmosphere. There appears to be evidence for photochemical haze from a 2002 occultation (Elliott et al 2003) but occultations in 2007 and 2011 did not show evidence of this. Hazes are large particles in the atmosphere (almost cloud-like) and the 2002 occultation had suggested hazes since there had been a distinct change in brightness as a function of wavelength. Why does the haze come and go, and what is causing it?

Pluto has also indicated “reddening” (color-change) that occurred between 2000 and 2002 (Marc Buie using color photometry with HST). That’s a mystery.

Waves (dynamic changes) in atmosphere are indicated by some of the occultation measurements. What could cause waves? There are multiple suggestions what could form these dynamic changes (even evoking the elusive gravity wave mechanism). Could it simply be Pluto’s atmosphere response due to the diurnal variation of sublimation of N2 particles?

What will Pluto’s Atmosphere be like when New Horizons comes to take a close look?

  • Will the atmosphere be there in 2015? Lellouch’s best guess: Yes.
  • Will there be a thermal structure (i.e. see a troposphere)? Lellouch’s best guess: Hopefully (helps modelers out).
  • Will there be other gases present (i.e. C2H2 HCN, etc.)? Lellouch’s best guess: Maybe.
  • Will there be clouds or hazes? Lellouch’s best guess: Maybe.
  • When will the atmosphere collapse (i.e. pressure drops by orders of magnitude)? Lellouch’s best guess: “Your guess is as good as mine.”

Comparative compositions of Pluto and friends, even long-distant friends.

Continuing coverage of the July 22, 2013 first day of the Pluto Science Conference being held this week in Laurel, MD.

Bill McKinnon (Washington University) next provided an engaging talk about implications for composition and structure for Pluto and Charon.

Where did Pluto Accrete (i.e. where was Pluto born)? Pluto is not alone in its location on that a/e plot for Trans-Neptunian Objects (see previous posting).  It’s part of an ensemble of bodies on the 2:3 resonance with Neptune, coined the group “Plutinos.” Was Pluto formed around 33 AU (Malhotra 1993, 1995) and then migrated outward? What does this Nice I Model (Levinson et al 2008) which migrates the giant planets predict for the KBO population? The Nice I Model implies that for Pluto, Pluto could have formed 20-29 AU (i.e. closer in) to allow it to achieve its high inclination. Then a subsequent model, Nice II (Levinson et al 2011), suggests Pluto may have formed in the 15-34 AU range. This is in okay-agreement with accretion models since Pluto, a 1000-km size body, would need 5-10 million years (i.e. within a nebular life) if it were formed in the 20-25 AU range. McKinnon’s best guess: Pluto formed between 15-30 AU.

How long did accretion take and what are the implications (i.e. how long for Pluto to grow up)? If we have an accretion time (10’s of million years), there is time enough to form Aluminum-26, which provides a form of heat through its decay. Heat then can melt ices and create a differentiated body (i.e., rocky core, icy mantle) and also drive water out. McKinnon’s best guess: Pluto formed rapidly and early.

What are Pluto & Charon made of? They are understood to be made of rock+metal, volatile ices, and organics, with rock+metal more than ice, and ice more than organics. The rock will be some combination of hydrated & anhydrous silicates, sulfides, oxides, carbonates, chondrules, CAIs (calcium-aluminum-rich inclusions), CHONPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur). We don’t really know what sort of composition these KBO volatile ices: will they be more like Jupiter Family Comets or Oort Comets? And we know even less about organic components: will the Nitrogen to Carbon ratio tell us whether KBO N2 (nitrogen) comes from organics rather than NH3 (ammonia)? Solar models (which lock up CO (carbon-monoxide) into carbon) can influence understanding of what rocks in the outer solar system are made of but their models are not in agreement with the best understanding of Pluto/Charon make-up. McKinnon’s best guess: Rock/Ice nature of Pluto-Charon is 70/30.

What are the implications for Pluto & Charon internal structure? New Horizons will not directly detect the differentiation state of Pluto & Charon because it does not fly close enough.

Alain Doressoundiram (Paris, France) came next. Using MIOSTYS, multi-fiber front-end to a fast EMCCD camera, on a 193 cm telescope in France, they observe outer solar system bodies using stellar occultations. Other science objectives for variable stars, transiting exoplanets. They confirmed two TNO occultation events, one in 2009 and one in 2012 and continue monitoring.

Luke Burkhart (Johns Hopkins University) talked about his work on a “Non-linear satellite search around Haumea.” Haumea is another Trans-Neptunian Object (TNO) that has multiple satellite companion, like Pluto. Using HST (10 orbits) they observed the Haumea system and used a method of stacking & shifting to identify satellites. But this method fails to capture objects which are close in, moving fast, and on highly curved orbits. So they developed a new method using a non-linear shift-rate. Their approach, when applied to the Haumea system, had a null-result. However, this approach could be used on images of the Pluto system and other TNOs.  Specifically, in answer to a question from the audience, Luke would be eager to use his technique on any of those long-range KBO targets the New Horizons project is currently investigating.

Family portraits of the eight largest trans-Neptunian objects (TNOs).

Family portraits of the eight largest trans-Neptunian objects (TNOs) (From Pluto is shown with its 5 companions.

Andy Rivkin (JHU/APL) ended the afternoon’s lively discussion by addressingDistant Cousins: What the Asteroids Can Teach us About the Pluto System”. He started his talk with a comparison of sizes between Ceres (the largest asteroid in the asteroid belt between Mars and Jupiter) and the Pluto System. He used as his framework Emily Lakdawalla’s chart, which can be found on the Planetary Society blog

Here the relative sizes of objects in the Pluto system are represented by objects from the Saturn system. Saturn’s moon Rhea serves as Pluto, Dione as Charon, Prometheus as Nix, Pandora as Hydra, Helene as Kerberos, and Telesto as Styx. Superimposed is where Ceres (an asteroid in our asteroid belt between Jupiter & Mars) fits on this scale. Andy Rivkin did a comparison of his observations of Ceres to postulate what that might mean for the Pluto system.

Pluto system and Ceres shown to scale, represented by objects from the Saturn system.

Pluto system and Ceres shown to scale, represented by objects from the Saturn system.

Ceres has an icy interior, but much too warm to keep ice on surface. HST images reveals rather smooth surface. IR spectra (from reflected sunlight) are very rich and indicative of ice-type features. Could there some sort of layering? On Pluto, you could have the same thing, but it’s also cold enough for ice to remain on the surface. There is also a mystery that several large C asteroids have similar 3 micron spectra to Ceres like 10 Hygiea and 704 Interamnia.

Implications for Pluto: Large main-belt asteroids could serve as comparisons for KBOs. Geophysical comparisons may be easier than compositional ones.

So the big take-away from the introductory talks on the “Kuiper Belt Context” is that we can learn more by sharing the knowledge: Learning from Other Bodies  (Other TNOs, Comets, Asteroids) will help us learn more about Pluto & Charon, and vice versa.

Finding that distant KBO needle in a deep space haystack.

Next up at the Pluto Science Conference were a series of talks dedicated to recent work in the searches for another Kuiper Belt Object (KBO) for the New Horizons spacecraft to fly by after its Pluto fly-by. Fuel on board the New Horizons spacecraft after the July 2015 Pluto fly-by could enable a fly-by of a distant KBO in the late 2010s through 2020s, pending identification of targets reachable within New Horizon’s remaining fuel budget.

John Spencer (SwRI) has been leading the ground based campaign to search for New Horizons’ next target. With an on board ~0.13 km/s delta-v (measure of propellant), traveling at 14 km/s, this translated to a ~0.5 deg half-angle cone through the Kuiper Belt for accessible targets, a type of “survey beam.” Previous KBO searches had been for R>26.0 over 1-2 degrees. But right now Pluto is in Sagittarius which is in the direction of the Galactic Center and there are a lot of other stars in the field that make searching for a slowly-moving object, this KBO, difficult.

KBO Survey Star Field

Above are what the star fields the team is inspecting look like. They observe the same star field night after night and look for shifts in a object between frames, indicating it’s a KBO and not one of the “fixed stars.”

Outer Solar System“Known objects in the Kuiper belt, derived from data from the Minor Planet Center. The pronounced gap at the bottom is due to difficulties in detection against the background of the plane of the Milky Way.” This is exactly where John Spencer and his team are focusing their efforts because a subsection of that part of the sky is what is reachable by the New Horizons spacecraft after 2015. Image taken from

The ground based search program area is entering a sweet spot, where they can cover a smaller area of sky from the Earth that falls within the expected New Horizons travel zone.

KBO Search Zone

The team has found 31 objects from 2011 data including a TNO. However, as of 2012 season, they have not found an object that could have a fly-by encounter by the New Horizons spacecraft.  But there are three objects (2011 JW31, 2011 JY31, 2011 HZ102) that New Horizons could get to within 0.15-0.2 AU of in 2018-2019. The team is in the middle of the 2013 observing season and based on the current number densities they are predicting to see 1.78 objects down to  R=26.0mag and 4.15 objects in 26.5 mag.

Alex Parker (one more month at Harvard before moving to Berkeley) provided a more in depth view of unique observations New Horizons can still make of these long-distance KBO fly-by, that is, a fly-by in the 0.1-0.2 AU range of the spacecraft. At 0.2 AU range, New Horizons’ LORRI will have 140 km/pixel range compared to our “sharpest eyes” by Hubble at 1200 km /pixel from low-Earth orbit.

His excitement over the unique discovery space New Horizons provides that you cannot get from anywhere else: Proximity. High angular resolution. High phase angles.

He’s been studying trans-Neptunian binaries as binaries provide a direct mechanism to measure their masses. “Wide” Kuiper Belt binaries have been discovered already (e.g.  Gemini observations of wide binaries 2006 BR284 separated by 0.82 arcseconds; 2000 CF105 separated by 0.95 arcseconds).

To visualize a ride on looking over the New Horizons shoulders as it journeys into the Kuiper belt, check out this one of Alex Parker’s visualizations at

Make note to hold onto your seat when the craft enters the Cold Kuiper Belt region in 2018!

Susan Benecchi (Carnegie Institute) rounded out the talks with HST Follow-Up Observations of Long-Range Candidates for New Horizons post Pluto. They observed 2011 JW31, 2011 JY31, and 2011 HZ102 with HST. Those objects had been detected with the KBO ground based search program described by John Spencer and Alex Parker (previous presentations). Her team has not confirmed detection of 2011 JW31. Her team has confirmed the colors of the two other objects being “red” which is consistent with the Cold Classical Population (i.e. primordial). Implications for New Horizons: HST can provide this extra characterization step for new candidates.

Gustavo Beneditti-Rossi (Brazil) described a summary of “Astrometric Analysis of 15 years of Pluto Observations.” Using the Pico dos Dias Observatory (1.6m and 0.6m telescopes), they monitored Pluto-Charon (which is not separated in their data) for 154 nights over 1995 to 2012. They do refraction correction (due to viewing angle from earth) and photo-center correction (due to the fact they cannot separate Pluto from Charon). And show that their tracking of Pluto’s location is in agreement with occultation data.

To end this post, I could not resist showing you Alex Parker’s vision of what New Horizons brings to this field of study. He created this montage of images illustrating the proximity (within artistic license) and equally important the high phase (objects as crescents) and high angular resolution (we can see surface features), all that New Horizons will provide in 2015 that no other observation platform can.

NH Silhouette

2015 will be the “Year of Pluto” and so much more!

Pluto, “King of the Kuiper Belt, Prince of the Plutinos.” Certainly an object that inspires odes, songs, and ballads.

After the New Horizons’ instrument overviews on the first day at the Pluto Science Conference (Jul 22, 2013, we jumped right into Pluto in the Kuiper Belt Context.

Brett Gladman (University of British Columbia, Vancouver, Canada) started the conversation by addressing “How does Pluto fit in our understanding of the Kuiper Belt?”

But before we get into that, discussing the Kuiper belt today can be pretty complex. It was only discovered in 1992, but in the years since, over 130,000 bodies with sizes 100 km and larger have been identified (Petit et al 2011), with Pluto being the largest member.

So when we start looking at large numbers of objects, it’s time to classify. So a typical plot to describe these “populations” is shown below, where semi-major axis (distance of body from the Sun) is plotted (horizontal axis, labeled ‘a’ in units AU, where 1 AU is the distance of the Earth from the Sun, Jupiter is ~5 AU, Saturn ~10AU) versus eccentricity (value between 0 and 1 that describes how circular an orbit it, e=0 is circle, e=1 is parabola, 0<e<1 describes ovals).

And then you have your Classical, your Cold Classical, Hot Classical, Detached, Resonant, and SDO (aka Scattered Disk Objects), etc. Sometimes they group together, others are more uniform across the parameter space.

“Kuiper Belt in a/e space.”

Kuiper Belt in a/e space.” Cold classical (black open triangles). Resonant Kuiper (open red square). Detached (blue triangles). Pluto is indicated with the yellow-box, it’s a Resonant, as it is in 3:2 Resonance with Neptune. This group of objects, all in 3:2 Resonance with Neptune are the “Plutinos.” (that clumping around 40 AU, red triangles, spanning over a range of e). Resonance numbers are shown at the top of the graph.

Plutinos are also a family of TNOs, Trans-Neptunian Objects, characterized by being in 3:2 mean-motion resonance with Neptune (i.e., every time Neptune makes 3 trips about the Sun, the Plutinos make 2 trips). Plutinos are the most dominant of the TNOs. Less numerous are the 1:1 objects, objects known as Trojans.

Definitely KBO soup!

For more information about TNOs and their period relationships with Neptune

After getting down those nomenclature basics, Brett Gladman (who is also lead for a huge ground-based survey of KBOs called the Canada-France Ecliptic Plane Survey/CFEPS) discussed the strengths and pitfalls of the theories put forward to explain the formation and structure of this complex KBO menagerie.

For more information about CFEPS check out

How did Pluto get to where it is today? Two leading theories (1) Resonant sweeping of objects formed in TNO regions and (2) resonant trapping explain many things, but no published models explain those resonant structures of the Kuiper belt. And any of these models have issues with the classical and scattering disk populations as well. Theorists, better sharpen your pencils.

So he left us with questions to ponder. Is there a cold primordial Kuiper Belt with edge at 45 AU? Did Pluto likely form as one of hundreds to thousands of >1000km embryos? Did some of these become implanted into the nearby non-scattering belt? Are there others out beyond 100 AU (considered likely, but to discover them, you need to get down to 23-24th mag which is beyond the current survey capabilities until new telescopes and.or techniques come available)?

No doubt, searches for more TNOs will continue, the classification of the KB will undergo evolution, and theorists will refine their models. And New Horizons will provide a unique data set of an up-close-and-personal visit to Pluto and its companions to help constrain those models.

Putting Centaurs and TNOs in Context

Putting Centaurs and TNOs in Context. This time plotting inclination (the degrees from the ecliptic plane) vs. semi-major axis in AU. Object sizes are reflected in the symbol sizes. Location of Saturn, Uranus and Neptune are shown. Just another way to look at that awesome & diverse Outer Solar System. From:

Next, Cesar Fuentes (Arizona State) phoned in about his work on the “Size Distribution (SD) of the Kuiper Belt.” Size distribution is basically counting the number of objects as a function of size.  Coagulation (of small particles) and gravitation instability (of larger particles) shape the size distribution. Size distribution is expected to change due to collisions. Different distances from the sun also appear to have different size distributions.

He stepped us through recent size distribution models from Schlichting, Fuentes & Trilling (2013) and Kenyon & Bromley (2013) where they even have some including the “collisional factor” influence on the size distribution over time periods.

Snapshot of Size distributions by KBO-classification

All the Size Distributions show a “rollover” around H~9, D=70km. Nesvorny et al. 2013 investigates this further. Is the break due to collisional and therefore separate the primordial from the evolved KBO populations?

Even more questions to ponder:  Can we use size distributions to evaluate primordial from the evolved KBO populations?

And then he left us with a tantalizing experiment with the New Horizons mission: If New Horizons can provide data sets enabling “crater counting,” we will be able to measure the impactors on Pluto. This can aid in understanding KBO populations, addressing specifically, formation time, timescales for surface activity, and origins of bodies like Nix & Hydra. What would a 0.1-100 km impactor size distribution look like?

Pluto, be it Prince of the Plutinos or King of the Kuiper Belt, will always remain a key part to these questions above. And data sets from New Horizons will provide many new angles to answering questions about “Where did Pluto form and why did it wind up where it is now.”


Introducing the New Horizons Instrument Menagerie.

During the first day of the Pluto Science Conference, being held July 22-26, 2013, in Laurel, MD, the conference participants listened to a series of talks describing the rich instrument suite aboard the New Horizons Spacecraft. This entry is just a very brief synopsis of the instruments.

Ralph, Alice, MVIC, LEISA, LORRI, REX, SWAP, PEPSSI, SDC. Those are instrument names and acronyms of the New Horizons science instruments.

New Horizons Instrument SuiteNew Horizons Instrument Suite at a Glance.

LORRI (Long Range Reconnaissance Imager), among many things, “Enables Far-Out Encounter Science. ” That is, at 10 weeks from closest approach, LORRI can observe the Pluto system with spatial resolution better than Hubble. It is a visible camera, equipped with a 1024 x 1024 pixel CCD, with a 0.29 x 0.29 degree field of view (5 microradian pixel iFOV). LORRI also will be used, on approach, for optical navigation. The LORRI Instrument Principal Investigator and Instrument Scientist is Andy Cheng (JHU/APL) and Hal Weaver (JHU/APL), respectively.

Ralph & Alice form New Horizons’  “Remote Science Suite.” Ralph is both a color-imager (MVIC) and an infrared mapping spectrometer (LEISA). Alice is a ultraviolet spectrometer.

Ralph’s MVIC (Multi-Spectral Visible Imaging Camera) consists of seven independent CCD arrays. Four channels are filtered to map blue (400-550 nm), red (540-700 nm), near infrared (780-975 nm) and a narrow methane absorption band (860-910 nm). Six of the MVIC arrays (including all the filter channels) have a 5.7 x 0.037 degree field of view (20 microradian pixel iFOV). LEISA (Linear Etalon Imaging Spectral Array) is a grating spectrometer covering 1.25 to 2.5 microns wavelength range at a resolving power of R~240. A second segment covers 2.1 to 2.25 micron range with a resolving power of R~560. The Ralph Instrument Principal Investigator and Instrument Scientist is Alan Stern (SwRI) and Dennis Reuter (NASA Goddard), respectively.

Alice is an ultraviolet imaging spectrometer. It has two entrance apertures, a large airglow channel and a small SOCC aperture for solar occultation measurements. The entrance slit has two sections, a “box” with a 2.0 x 2.0 degree field of view, and a “stem” with a 0.1 x 4.0 degree field of view. The wavelength coverage spans from 520 to 1870 Angstroms, with a resolution of 3.6 Angstroms.  The Alice Instrument Principal Investigator and Instrument Scientist is Alan Stern (SwRI) and Maarten ver Steeg (SwRI, San Antonio), respectively.

REX, New Horizons’ Radio Science Experiment, is enabled by adding a small amount of signal processing hardware to the existing communication hardware on New Horizons’ main antenna. It will be used, among other observations of Pluto, to showcase a “Different Kind of Radioscience” via 20kW uplink experiments from the DSN during the Pluto and Charon occulations at flyby. The REX Principal Investigator and Instrument Scientist are G.L. Tyler and Ivan Linscott (Stanford University), respectively.

PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation) & SWAP (Solar Wind Around Pluto) are modern particle instruments designed to capture Pluto’s interaction with the solar wind. PEPSSI can measure ions and electrons from 10s of keV to 1 MeV over a 160 x 12 degree fan-shapped beam. SWAP can measure particles with energies 35 eV to 7.5 keV over a 276 x 10 degree field of view. PEPSSI’s Principal Investigator and Instrument Scientist are Ralph Mcnutt (JHU/APL) and Matthew Hill (JHU/APL). SWAP’s Principal Investigaor and Instrument Scientist are David McComas (SwRI, San Antonio) and Heather Elliott (SwRI, San Antonio).

SDC, the Student Dust Counter, designed and built by students at the University of Colorado, Boulder, is “The First Student Experiment on a Deep-Space Probe.” The Principal Investigator is Mihaly Horanyi (University of Colorado). There have been numerous Instrument Scientists, all students at Univ. of Colorado. The current Instrument Scientist is Jamey Szalay. Students continue to be active in supporting data analysis as SDC collects dust rates on its voyage through the solar system. More information about the SDC and the students behind it at

More details about each of the instrument descriptions and performance can be found at
New Horizons Instruments

Locations of the science instruments on the New Horizons Spacecraft

The Architecture of New Horizons’ Pluto Fly-By Sequence.

In her presentation at the Pluto Science Conference, Dr. Leslie Young (SwRI), deputy Project Scientist and chief architect of the Pluto Encounter Sequence, stepped us through the New Horizons’ Science Objectives and the types of observations that will be pre-programmed aboard the craft for the entire year of 2015. Unique science is not just around Pluto Closest Approach on Tues, Jul 14, 2015, but many months prior and post the encounter. Although most of the “Group 1” (see below for description) science objectives for the mission will be met by measurements made in the -2hr to +3hr from closest approach. Closest approach is on July 14, 2015.

Leslie Young Presents Group Science Objectives

Leslie Young (deputy Project Scientist) describes the overview of the science highlights for the year 2015. Also shown in the slide is a mapping of the Science Objectives per each phase.

Science space missions typically have a set of “science requirements,” specific measurements to address specific questions, set forth to be met by the mission design. The main science questions that the New Horizons mission is designed to answer were asked in the proposal call (AO 01-OSS-01) that NASA put out in early 2001, the competition which the New Horizons team won. The proposed series of measurements that New Horizons will do with its instrument suite provide measurements to answer Group 1, Group 2 or Group 3 objectives. Group 1 are measurements that must be done and define baseline science mission success. Group 2 are highly desired measurements and Group 3 are desired measurements. To obtain data that meets Group 1, 2 & 3 measurements is full-science success.

That single slide that Leslie showed (above) is the sum of many, many, many months of work with the New Horizons Science Team, along with support from the project’s Mission Design team, to identify which measurements of which body at which time (or times), as an ensemble meet the Group objectives. She specifically calls out the Group 1 by showing those categories in Bold Italics.

As the New Horizons Science Fly-By mission is a temporal series of measurements, the mission has been constructed to compartmentalize the measurements as a function of day from the closest approach. Hundreds of unique measurements are scheduled in rapid-formation within the day prior and after closest approach, called the NEP or Near Encounter Period.

Some Pluto Encounter Design Temporal Terminology:
AP= Approach Phase, NEP=Near Encounter Period, DP=Departure Phase
AP1: Jan 6-Apr 4, 2015, P-180 to P-100 days to Closest Approach
AP2: Apr 4-Jun 23, 2015, P-100 to P-21 days to Closest Approach
AP3: Jun 23-Jul 13, 2015, P-21 to P-1 days to Closest Approach
NEP: Jul 13-15, 2015, P-1 to P+1 day from Closest Approach
DP1: Jul 15-Aug 4, 2015, P+1 to P+21 days from Closest Approach
DP2: Aug 5-Oct 22, 2015, P+21 to P+100 days from Closest Approach
DP3: Oct 22, 2015-Jan 1, 2016, P+100 to P+180 days from Closest Approach

Leslie Young Present Near Encounter Phase

Leslie Young describes the mission science measurements on a timeline near closest-approach. The instruments are color-coded in this representation of the distance to Pluto (y axis) vs. distance from Earth/Sun (x axis) with respect to the closest approach (nominal July 14, 2015 11:50 UTC). A larger version of that slide is shown below. The x-axis spans 5 hrs of time.

NEP Timeline

Below is a summary of the best spatial resolution measurements anticipated from New Horizons’ Remote Sensing Suite within a few hours of closest approach. Panchromatic (LORRI camera), Color (Ralph MVIC), and Infrared (Ralph LEISA) resolutions are shown against each target body for the closest-distance to those target bodies in the nominal sequence. The science requirement for the equivalent Group 1 objective is shown in italicized text.

NH Best Resolution Specs

With our current best resolution of Pluto spanning 100 km/pixels taken with the Hubble Space Telescope, the New Horizons mission with its up-close-and-person will rewrite the textbooks on this elusive system with more than 2 orders of magnitude resolution improvement, plus spectral, radioscience, and plasma unique measurements.

Our best on Pluto from Hubble can be found form these links for observations taken in 1994 & 2010: and, respectively.

Calling for proposals to observe the Pluto System from Earth and Earth satellite-assets! “As planetary astronomers, we love phases” as Rick Binzel (MIT) describes “Earth-Based Observing Campaign for the New Horizons Encounter.” We’re going to need to make a link to connect decades of earth-based observations of the Pluto system before the fly-by and continue it for decades after the New Horizons fly-by. There is a website set up for information on how to participate and get more information. Specifically observations are needed in 2014, 2015 (encounter year), and 2016.

Earth Campain Obs Pluto

The website will be based at . Check back later since they are actively working the content, but you can always email nhobs “at” for information.

Rick Binzel also introduced the campaign to get a Lego set made of the New Horizons Spacecraft. It needs to vote to get it approved for production. Note: this requires you to register for free-account to log in to vote.

NH Lego

Summing up the first session of an exciting beginning to the Pluto Science Conference,  per Alan Stern, the Principal Investigator for NASA’s New Horizons’ Mission: “The most exciting discoveries will likely be the ones we don’t anticipate” and  “Revolution in Knowledge is in Store.”

Initial Reconnaissance of the Solar System’s Third Zone.

This is part of a blog series on the Pluto Science Conference, “The Pluto System on the Eve of Exploration by New Horizons: Perspectives and Predictions,” held July 22-26, 2013 in Laurel, MD.

New Horizons’ Principal InvAlan Stern Overview Talk Pluto Science Conferenceestigator (lead scientist) is Dr Alan Stern (SwRI/Southwest Research Institute). In his presentation, he gave an overview of the mission concept, the science objectives and mission status. The scientific suite is sophisticated and carries the first student-built deep space instrument. The cruise period spans two Presidential administrations (8 years). New Horizons launched on January 19, 2006, and will fly by the Pluto system with closest approach July 14, 2015. For more information about the mission, do check out the New Horizons Mission Websites: (JHU APL site) and (NASA site).

New Horizons Trajectory OverViewAt a glance, the New Horizons Mission to Pluto and Beyond. Key milestone dates and the spacecraft trajectory (in red).

Measurement-wise, New Horizons’ Pluto fly-by of July 2015 is comparable to Voyager 2’s fly-by of Neptune’s moon Triton in 1989. However, Voyager 2 did not have an infrared mapping nor ultraviolet imaging spectrometer, something New Horizons will have. Also, New Horizons will be flying three times closer to Pluto than Voyager 2 did at Triton.  A snapshot of the comparison highlights from Alan’s talk is below.

Triton & Pluto at Best HST Resolution and Triton from Voyager with the visualization of what Pluto’s best resolution from New Horizons

Comparison of Voyager 2 data from its fly-by of Neptune’s moon Triton in August 1989, with a “visualization” of what New Horizons’ best resolution at Pluto might reveal during its fly-by of Pluto in July 2015.

The New Horizons’ unique science encounter involves more than 6 months of active science operations, starting in mid-April 2015 when the on-board instrument suite achieves resolution better than Hubble.

A more in depth discussion about “When will New Horizons have better views of Pluto than Hubble does?” can be found in this blog entry on the Planetary Society’s blog site at .

For more in-depth information about the New Horizons mission check out a series of a papers published in Space Science Reviews.  Link:

To end this posting, a few fun factoids about New Horizon’s Speedy Performance since Launch.
New Horizons’ Speed Record. Launched on an Atlas V-551 on January 19, 2006 at 14:00 EST, the ~400 kg spacecraft, about the size of a grand-piano, needs to travel 5 billion km (5x10e9 km) from Earth before it can execute the observations for its prime science mission. Launching with a speed of  58,000 km/hr (36,000 mph) and benefiting from a gravity-assist from Jupiter in February 2007 (which boosted the spacecraft speed), New Horizons will reach its destination, Pluto, after ~9.5 years of space flight.

New Horizons Speed Facts:
Launched at 36,000 mph
Passed Moon’s orbit in 9 hours
Passed orbits of:
Mars on 4/7/2006
Jupiter on 2/28/2007
Saturn on 6/8/2008
Uranus on 3/18/2011
To cross orbit of:
Neptune on 8/24/2014
With closest Approach Pluto-Charon on 7/14/2015

New Horizons, a mission for the patient (and persistent).

New Horizons is a Mission for the Patient (and Persistent). It is a labor of love, dedication, fortitude, with compelling science, top-notch engineering, and tight management. This is an entry part of a blog series covering the Pluto Science Conference, held July 22-26, 2013 in Laurel, MD.

Tom Krimigis (JHU/APL) started off our excited Pluto crowd with an overview of the steps that enabled the New Horizons mission to become reality. Any science mission starts with its science objectives. Successful science mission concepts that make it to launch rely on thorough reviews of its science, engineering, and investment (i.e. cost & feasibility).  New Horizons, owes its existence to both initial scientific grounding work by the scientists in the 1970s and equally also to the persistence of those scientists and supporters at NASA and Congress over the subsequent decades to make it get to flight. New Horizons was selected in November 2001 from a competition and launched in January 2006. It will reach its destination, the Pluto-Charon system in 2015.

A rose by any other name is still a rose. A mission to Pluto has had many names over these past decades and with concepts “varying on a theme.” It was called Mariner-Jupiter-Pluto (MJP), mini Voyager-Pluto Fast Flyby (PFF), Pluto Express-Pluto-Kuiper Express, and now New Horizons, among many mission names.

For more reading about the saga, science, and significance of Pluto exploration, check out Andrew Lawler, Science 295, 32-36, Jan 4, 2002. “Planetary Science’s Defining Moment.” at  (requires login access) or find it herefrom the author’ website here.

Pluto Not Yet Explored. US Stamp Series 1992

Pluto Not Yet Explored (lower right) from USPS Stamp Series (1991)

Introducing the Pluto Science Conference July 22-26, 2013.

The mind of a scientist understands, embraces, and executes the scientific method, the process by which an idea is created, then tested by experiment or model, validated or refuted, and then, when validated, culminates in the description of the results to the larger community through a publication. The cycle begins again, sometimes building on previously published work, or in some cases, the birth of new ideas to the scene, most likely inspired by previous knowledge.

A key component to a scientist’s work is the attendance and interaction with colleagues at scientific conferences. At such gatherings we can see examples of the scientific method in a multitude of stages: the birth of a new idea, the suggestion of methods to carry-out the experiment or computation, a presentation that disproves an approach requiring the scientist to start anew, through the description of the results of the recent experiment or computation.

~150 people are to gather this week at the Johns Hopkins University Applied Physics Laboratory in Laurel, MD to share ideas, debate hypotheses, and explain experiments related to the emissary from our Solar System’s Third Zone, the dwarf planet Pluto and its moons. The timing is crucial to have these conversations because in two years from now, in July 2015, NASA’s New Horizons Spacecraft will do a close fly-by of the Pluto system, a system never before visited by another spacecraft. The forum provides an update of the mission and its measurement capabilities and encourages healthy dialog among theorists who have predictions, laboratory spectroscopists who can build examples of chemistry happening on these icy bodies, and observers who have been monitoring and documenting the changing nature of Pluto and its environment.

Details about the Pluto Science Conference, “The Pluto System on the Eve of Exploration by New Horizons: Perspectives and Predictions,” can be found here at

You can follow the New Horizons mission status at any time by visiting the New Horizons Mission Website at and

I’ll be providing summaries of the meeting content and discussions through a series of blog posts this week. For now, I’ll leave you with some things we do know about Pluto and its largest moon Charon.

The diameters of Pluto & Charon shown with respect to the USA for scale

The diameters of Pluto & Charon shown with respect to the USA for scale.

What do we know about Pluto so far?

  • Highly elliptical (e = 0.25), Highly inclined (i = 17 deg), 248 year orbit
  •  Rotational period of 6.387230 days
  •  Small (diameter = 2328 ± 42 km), Rock/Ice object (“Icy Dwarf”)
  •  Density is 2.03 ± 0.06 g cm-3, Mass = 0.0022 MEarth
  •  Bright surface frosts of N2, CH4, CO, and C2H6  produce albedo of ~55%
  •  Highly variegated surface (bright and dark regions)
  •  Reddish in color, probably due to surface organics
  •  Tenuous, variable atmosphere (mostly N2; 2-10 µbars at the surface & going up)

What do we know about Charon?

  • Discovered, by accident, in July 1978 by James Christy (USNO)
  •  In circular orbit ~19,573 km from Pluto, with a 6.3872273 day period
  •  Tidally-locked spin period (i.e., spin-orbit synchronous)
  •  Diameter is 1212 ± 3 km (about half of Pluto’s Diameter: “Binary Planet”)
  •  Density is 1.66 ± 0.06 g cm-3 (vs 2.03 ± 0.06 g cm-3 for Pluto)
  •  Surface has crystalline H2O-ice and NH3-hydrate (recent?)
  •  Average albedo ~35%, neutral color (variegation change over time?)
  •  Average T ~ 50 K, low thermal inertia (high porosity)
  •  No atmosphere detected yet (~10-300x lower pressure than Pluto’s)

Charon Discovery Image 1978New Horizon’s LORRI instrument spots Charon Jul 3, 2013 from 6AU away

(left) Charon Discovery Image July 1978; (right) New Horizons’ LORRI instrument spots Charon July 2013 from 6AU away.

To Pluto and beyond!

Reflections on flying on SOFIA. I totally got the SOFIA bug.

Tonight, Thurs Jun 13th was to be a second opportunity for me to fly and test the FORCAST grism suite on SOFIA. However, that flight had a RTB or return to base, due to an aircraft item that manifest itself inflight. The pilots were awesome and returned us back to Palmdale, CA, safely.They followed their checklists and since most of tonight’s flight was to be thousands of miles over the Pacific, return to base was the right course of action. The flight is now rescheduled for next Tuesday. I am hoping I can remain on the passenger manifest and I can always do remote support.

For those who follow the SOFIA story, it has been a longtime coming. But you just have to admit it, SOFIA is just cool. First of all,airplanes are cool. 747s are even cooler. And to have a hole cut into a 747 to outfit it with a telescope that can point, even in turbulence, is just the coolest of coolness. I know I always knew that, but in all honestly, I did not realize it until I experienced it. I hope you have enjoyed my blog updates on this experience.

SOFIA is also an amazing piece of engineering. If you think about it, a lot of engineering has gone into the airplane, the modifications to support the telescope, the telescope design and operation, all the different science instruments, and the support infrastructure to make it all happen.Thanks to all the people who made this unique observatory possible, and those that are working hard today getting it operational.

For those astronomers out there, a call is on the street for science observing on SOFIA. Proposals are due Jun 28th, 2013 for the 2014 observing cycle.

For those interested in applying to be SOFIA Airborne Ambassadors, definitely check out that amazing program. The current application period is closed. But check in the future for the next call.

SOFIA is a powerful observatory. Its legacy is about to happen. There are not many telescopes out there that can access the infrared skies. By flying above the water vapor in our atmosphere, the infrared sky is revealed to us. Of course, our eyes cannot see such wavelengths, but our infrared detectors can. We can use these tools on SOFIA to answer questions about the formation of the stars and galaxies and their evolution. SOFIA with its 20 year lifetime and its mobility to be operated from anywhere on the planet that has a runway, has only yet to contribute to understanding of what’s out there. It’s an excellent training platform for students and teachers. In fact, on the line ops and the flights I was on, teachers and undergraduate and graduate students participated. What a great opportunity for a grad student to have access to this state-of-the-art telescope! The four I have met these past few weeks are so jazzed about what they are going to observe with SOFIA.

SOFIA after the successful completion of Flight#105, the morning of Jun 12, 2013

SOFIA after the successful completion of Flight#105, the morning of Jun 12, 2013. We got over 8 hrs of time at >= 40,000ft checking out the modes to commission the FORCAST mid-infrared camera with grism complement.

I still have work to do on my small role in the SOFIA story. We collected some (not all) of our grism commissioning data. With next week’s flight, we aim to fill in those gaps. I have data now to reduce and check out our quicklook pipeline that we are tailoring for the observers who request to use of grisms to do their science. And, that long awaited paper on the actual performance of these novel infrared optics I helped develop is now in the works!

I look forward to flying again on SOFIA, as an observer. I have a few ideas of neat things to observe.

I close my blog series with an amusing observation. On my Jun11th flight, I spent most of my time facing the science instrument/telescope area, which is, towards the rear of the plane. I was standing a lot, and occasionally would sit down at the conference area mid-deck to do some data reduction. All that time I stood watching the telescope, participating in discussions about the data, etc. looking aft, I realized I was journeying on SOFIA, as viewed by someone outside the plane, backwards.

Terry Herter (Cornell), FORCAST Principal Investigator & many-time SOFIA flyer, remarked to me, “After a few minutes in the air, you forget you are in an airplane.” And that’s precisely that. I thought I was observing at a telescope observatory.  The only drawback: I could not walk outsideto look at the stars, as I just love to do when I am a dark site, like at an observatory. But that’s okay, I was using state-of-the-art instruments to look at the stars with a different set of infrared eyes.

I’m not sure how the comments section on these blogs work, but I’d be happy to answer any questions. Just drop me a line.  Kimberly.Ennico at nasa dot gov.

The blog author aboard SOFIA during take off on Jun 13, 2013

The blog author aboard SOFIA during take off on Jun 13, 2013. Notebook in hand. Mind on the targets we were to observe that flight. Smile for the adventure and learning ahead.