Anne Verbiscer Colloquium Notes 2023/3/3

2023-March-03
P1 Notes by Luna Brannon
[Drawing of New Horizons Space Craft indicated in the outer half of the circumsolar dust disk.]
To ~~Infinity~~ 55AU AND BEYOND:
NEW HORIZONS' EXPLORATIONS FROM THE OUTER SOLAR SYSTEM
Colloquium Lecture by Dr. Anne Verbiscer @ HPU
Deputy Project Scientist, N.H. Kuiper Belt Extended Mission.

She does occultations w/ Jeff Regester. She worked on Voyager 2 & Cassini, and now New Horizons.

New Horizons woke up on March 1st 2023 for its extended mission.
7 Instruments: LORRI greyscale camera, RALPH visible & IR camera. REX does radio science & communications, and even works as a dust detector which can measure more dust than Venetia Burney Student Student Dust Cullector.
Solar Wind Analyzer At Pluto (SWAP) & PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation)
The latter two do solar science from 1 au on outwards.
Launch Jan 2006, Jupiter flyby 2007 Feb, Pluto flyby July 2015, KBOs 2016-2024 (Arrokoth, 2019)
Plan "Always was" to investigate Kuiper Belt.
Verbiscer's favorite image is the backlit haze Pluto, same as Dr. Cathy Olkin. [sketch of crescent Pluto with haze layers]

* Cold Classical KBOs have been unchanged for all of Solar System history.
--Oldest surfaces in solar system
* Plutinos have been "thrown around" a lot; centaurs even more so.
Search for targets for secondary mission started between 2004 & 2005, with difficulty since NH's flight path goes in front of the Milky Way.
Hubble found 3 potential targets for NH extension, 1st target, PT1 aka 2014 MU69, became the flyby target. "Arrokoth."
Arrokoth is the most primitive object we have seen in the solar system (the only Cold Classical KBO yet)

P2

Aside from close flybys, NEW HORIZONS continues to do science. [its onboard telescopes have a] mag 21 limit. It can do a lot of science w/ just a point of light due to existing in-situ rather than near Earth. It could see many nearby KBOs to Arrokoth (as points.)

Question [me writing intent to ask question]: is Eris in the right alignment w/ N.H. to get closer to it, or is even being farther away valuable?

[drawing of a bright gibbous/full disk labelled "from Earth 2 degree phase angle.] [drawing of narrower gibbous and crescent disk labelled "from NH. Any phase angle."]
NH sees different phase angles to measure differences in surface properties
* Single-Scattering Albedo
* Opposition surge
* Macroscopic roughness = slopes in topography of planetoid
* Directional [properties? parameters?] (backward or forward scattering)
* ALBEDO----------> bright: ices; dark: tholins, carbon, non-volatiles/rock
* Geometric Albedo (requires size measurement)
--Direct imaging w/ HST (large KBOs)
--Infer from apparent magnitude
--Stellar occultation--"great way to measure size."
--Thermal from Herschel, Spitzer, & ALMA.
   ALMA measured 15710 Arawn (the one from that awful pseudoscience documentary) which NH looked at.

NH can look at Rotation Light Curves at different phase angles!
The amplitude of light curve areas at different phase angles:
[graph showing two roughly sinusoidal curves. One has a higher amplitude than the other but the peaks and troughs are roughly aligned.] This allows you yo get a model of the KBO's shape.
Some do not change much across rotation & rotate slowly -- BINARY KBO! not split, not spectroscopic/doppler, but suspected due to light curve.

Arrokoth lacks a light curve due to pointing its pole at Earth (and at New Horizons on approach)
NH finds many other KBOs are also flat, high obliquity objects.
Light curve model is called D.A.M.I.T. [sketch of 2014 PN70, a thin wedge-shaped object a little thicker than Arrokoth but still very flat.]

Question [for later]: could 2014 PN70 be binary? [or can DAMIT rule that out?]

P3

There is a correlation between surface composition and phase light curves. [tiny cartoon graph. Y axis is magnitude, X axis is phase angle from 0 to 180 degrees. Three curves are drawn, each one decreasing in height towards the right side. The curve labelled "icy" is brighter and has a sharp cutoff at the end, the curve labelled "rocky" goes down quickly.]

No ices on Arrokoth, only methanol in small amounts. [Graph of light curves showing cold classicals are dark and quaoar is bright]

Subaru telescope [sketch of the observatory, sketch of big 3 ton camera on front of telescope]
CONTINUING SEARCH FOR NH TARGETS.

Bright newly discovered KBO disappears. Why? [this was meant to be a question to ask later but i didnt label it as such so i forgot about it. Has to do with a video of a KBO moving across a Subaru field and then winking out at the end of the video while the stars stay bright.]

New Horizons purchased a new Extreme Broadband Filter for Subaru to use to search for NH targets. (EB-Gri filter) Half magnitude deeper. Filter hasnt been used [since it was installed last October] because the search field is a summer sky (near sagittarius).

44,000 frames to sift thru w/ human eyes? No, let's use MACHINE LEARNING! Narrow down to perhaps ~100s instead of 10,000s.
Most new KBOs are "in the rear-view mirror."
13 were found in front of N.H. The spacecraft appears to be in a gap beyond the densest realm of KBOs, beyond which is a thinner disk. Preliminary, unconfirmed: does the Kuiper Belt6 have gaps like in images of circumstellar disks? Other searches away from galactic plane do not see this, but N.H. is looking into the galaxy which makes it difficult.

ODDS OF FINDING A KBO **IF** there is a gap that has already been passed, with a denser population ahead is about 1%. Less if the gap is systematic.

P4

EXTENDED MISSION focuses on HELIOPHYSICS via solar wind science [and dust], and astrophysics using cosmic rays. LORRI found a cosmic OPTICAL background, which is still a mystery. There's extra light outside of galactic plane.

ALICE instrument will build Lyman-Alpha map of sky. Student Dust Collector measures circumsolar dust and eventually interstellar dust. It's moving a different direction than Pioneer & Voyager, and is better equipped to measure.

"Funded or not, it's gonna keep going."

--------------Q&A-------------------

ERIS is in the wrong direction. Not much phase angle difference. JWST saw surface info in "real detail" in NIR.

N.H. communication for A LONG TIME. No reaction wheels on N.H., so limitation is fuel for pointing, rather than RTG or comms distance. Fuel must [be used to] stop spin, point, start spin, each time it makes observations.
Power for a long time--2030 originally, engineers can push to 2040 or even 2050.
<200 m/s or <120m/s reserved for corrections.
Arrokoth burned half of what remained.

DAMIT modelling assumes constant reflectivity--only works for Cold Classicals w/ uniform surface color.

Q: can DAMIT rule out contact binaries / concavities?
A: it should be able to.

[drawing of a light curve which looks like mcdonalds golden arches, with a sharp point in the middle and rounded peaks, labelled "Contact Binary light curve", drawing of a smoother more sinusoidal "m" shape labelled "regular elongated light curve."

2011 JX31 -oddball w/ a lot of uncertainty.