(=CIOC) SBAG Update Jan – Jul 2013
CIOC Team established Jan 2013 at SBAG-8. Team has a mix of experiences,
skillsets, and research specialties. Abundant contributions from early- and midSBAG scientists. Reports monthly to Lindley Johnson, Kelly Fast, and Jim Green.
Members chosen from SBAG: Lisse, Fernandez, Battams, Kelley, Knight, Vervack,
Warner, Yanamandra-Fisher, DiSanti.
Mantra: Facilitate, facilitate, facilitate. Bottom line is to maximize the science
returned from Comet ISON by involving every telescope in the solar system in ISON
CIOC Contact Info:
http://www.isoncampaign.org (Committee & news)
https://dnnpro.outer.jhuapl.edu/isonworkshop (Workshop)
CIOC Achievements/Products
NASA-NSF Opportunity Letter: e.g. SMA, GEMINI
NASA KECK Public Call - 12 partial nights scheduled (MOWG :)
NASA IRTF Public Call – 200 hours over 39 nights now scheduled
NSO Solar Telescope Observing: Sunspot/Dunn; KPNO/McMath-Pierce; Big Bear
Mars Fleet: MRO,MAVEN, Curiosity, Opportunity, Mars Express(?). Bonus: Observing
practice for Comet C/2013 A1 (Siding Spring) VERY close Mars approach in Oct 2014
Mercury Fleet: MESSENGER to Obtain Near-Planet Comparison to Comet 2P/Encke
Solar Fleet: Hinode, SDO, SOHO, STEREO, following up on Comet 2011 W3 (Lovejoy)
NASA Spacecraft (Astrophysics): SWIFT, Deep Impact, HST, Spitzer, Chandra
CIOC Website (information, news, links, no archiving) http://www.isoncampaign.org
NASA CIOC Facebook page, blogs; Amateur involvement; CARA & other “professional amateurs”
NASA HQ EPO: Ask an Astronomer; Media Point of Contact – e.g. NHK, Discovery Channel, BBC, etc.
CIOC WORKSHOP: Aug 1-2, 2013 at APL https://dnnpro.outer.jhuapl.edu/isonworkshop/Home.aspx
Comet ISON Observing Campaign Website
New CIOC Website Established:
- Latest news/updates about
the comet
- Updated lightcurve
- Workshop information
- Resources for amateur/proam/professional
- Blog posts from CIOC Team
Almost 3,000 pageviews in the
first week since launch!
Why Care About
C/ISON 2012 S1?
• First passage of comet through inner solar system since formation and ejection
-- Long arc from discovery and pre-discovery astrometry
-- More detailed dynamical studies thanEarth
most “dynamically new” comets
• On a Sungrazing Orbit
-- Discovered much earlier than any previous sungrazer
-- Perihelion Nov 28, 2013 at a distance of 2.7 solar radii
• ISON will have close encounters with Mars, Mercury, Sol, and Earth in 2013.
• This combination of fortuitous observing circumstances for a highly pristine
dynamically new Oort Cloud comet has not occurred in the modern era of
solar system exploration (that started 50 years ago with the Mariner 2 flyby of
C/ISON has likely spent the 4.5 Gyr since its formation far from the Sun and the
planets in the deep freeze of the Oort Cloud. For C/ISON to come from the
depths of the Cloud, with more than a year’s notice, at ~62o inclination to the
ecliptic and have close encounters with 3 of the 4 inner system planets and the
Sun is incredibly rare, practically unique.
C/ISON will provide an amazing spectacle and fantastic
observing opportunity for the best planetary seat in the solar
system, Mars, when it comes within 0.07 AU of the planet on 01
Oct 2013.
From J.Y. Li, APL
of Comets
w ill&
Solar telescopes
to Mars
Oct 2
J.-Y. Li, APL SRE Brownbag
Provided&by&M .&Knight7
MRO Observation Campaigns
• Campaign #1: sometime week of Aug 18-24
Characterize activity as comet crosses through water line
HiRISE: two scans but try to keep to 1 orbit
MCS, CRISM considering what their observation requirements would be
CTX/MARCI would ride along on what observations work for them
• Campaign #2: September 29 and October 2
Structure of the coma
Sept 29 is best viewing geometry for imaging, Oct 2 is C/A
Plan both days as a single campaign
HiRISE: three separate scans
MCS, CRISM considering what their observation requirements would be
CTX/MARCI would ride along on what observations work for them
Comet ISON will be extremely well placed for observations by solar
observatories in space and on the ground as it passes through
perihelion at q = 0.0125 AU on 28 Nov 2013. The comet will pass
within the coronagraph of the SOHO LASCO C3 camera shown here,
close enough to vaporize the refractory dust in its coma and tail.
Heliophysics spacecraft plans for ISON observations
- Will observe continuously in LASCO C3 and C2
coronagraphs from Nov 27-30.
- Requests have been made to DSN for extended
realtime coverage during critical times (e.g. entering
C3 fov and transiting C2) so that observations can be
adjusted to accommodate brightness, etc.
Will observe ISON from October 10 through perihelion
with heliospheric imagers, coronagraphs and EUV
imagers on twin spacecraft in different locations on the
far side of the Sun.
Currently plans to off-point to observe
the perihelion passage of ISON
Comet C/2012 S1 ISON: (Almost) Surely a Spectacular
Lovejoy in late 2012
Credit: Colin Legg
Expected view of ISON on Dec 10
Credit: Dave Eagle, www.eagleseye.me.uk
Detailed Comet ISON Scheduling at IRTF and Keck
Draft SBAG CIOC Findings
We find that a small group of comet experts working together
with NASA HQ, NASA's telescope assets, NASA's EPO teams, and
the scientific community to facilitate the maximal production of
scientific results during a bright comet's apparition is highly
useful. The creation of websites, workshops, and focused
scientific meetings has helped to improve communication
between interested observers and researchers and tailor future
measurements for maximal return, while keeping the public well
informed. A novel method of producing immediately public data
sets from the Keck and IRTF has been well subscribed, while s/c
projects (e.g. MRO, MESSENGER, SDO/SOHO/STEREO have been
actively contacted to help design, implement, and analyze ISON
observations during upcoming close passages of Mars, Mercury,
Sol, and the Earth.
ISON Science Results Slides
Results from the 10 April 2013 HST DDT observations of ISON. (Left) Li et al. (2013)
Coma + nucleus WFC3 F606W (R-band) image of the comet with a 1/p profile
removed, showing a simple, strong sunward asymmetry and trailing tail structure and
little variation during the three 45-min long visits performed over 19 hrs. Finding a
slowly varying coma dominated by emission from the (hottest) subsolar point is not
unreasonable for a simple unprocessed spherical comet nucleus. The HST WFC3 IFOV
is 40” x 40” wide. (Right) F438W/F606W 2-color map of the comet’s nucleus, coma,
and tail regions. Blue denotes regions of higher relative F438W emission, or bluer
material, and red denotes redder regions with higher F606W. There is a mystery here
– particle size changes caused by sublimation and fragmentation, decreasing the size
of emitted dust, should create bluer dust farther from the nucleus. (Gas emission lines
are not important in these filters, so we can focus on coma dust changes.) The best
alternative explanation is that very icy dust is being emitted from the nucleus, and the
ice is rapidly sublimating from this dust, leaving behind a redder remnant.
Dust Tail
HST 0.606 µm image taken on (4/10/2013) at rh = 4.4 AU vs. Spitzer
4.5 µm image taken on (6/13/2013) at rh = 3.35 AU, indicating the
large spatial extent of the extended neutral gas coma + anti-solar
dust tail. Scale Bar = 100,000 km.
3.6 um
4.5 um
4.5 - 3.6
C/2012 S1 (ISON): C.M. Lisse et al. report the detection of comet ISON using the Spitzer Space Telescope (SST) on
13.00 – 23.12 Jun UT at 3.6 um (left) and 4.5 um (center) when the comet was rh = 3.34 AU distant from the Sun, 3.29
AU from SST, and 4.25 AU from the Earth, well outside the water ice line.
ISON's Spitzer coma morphology was relatively compact and simple, with a linear anti-solar dust tail > 3x105 km in
length (left) and a 1/rho profile gas coma extending > 2 x 106 km from the nucleus (right).
No variability in our L-or M-band photometry at the 0.03 mag level over 24 hrs was seen.
First detection of neutral gas emission form ISON. Assuming a CO2 coma from a nuclear source with outflow at ~0.35
km/sec (Biver et al. 3/2013), Q(CO2) = 1.9 x 1026 mol/sec, and Rnuc > 0.09 km. Assuming the gas coma consists
primarily of CO from a nuclear source with outflow at ~0.35 km/sec, we find Q(CO) = 2.1 x 1027 mol/sec, and a
minimum nucleus effective radius of 0.17 km. (Lengthscales, |Qgas|, rh activity fit CO2 well.)
What We Currently Know About Comet ISON
• Dynamically New Sungrazing Comet on 1st Passage through Inner SS since its
formation 4.5 Gya. Exceptional inner planet “tour”.
• Small nucleus, 0.1 km < Rnuc < 2 km (needs > 0.5 km to survive 0.014 AU
• Active out to 8.3 AU, slightly inside the CO2 Ice Line.
• Linear Dust Tail (small, fine dust) + (CO/CO2) Gas Coma > 106 km in Extent
• Q(CO) ~ 2x1027 mol/sec or Q(CO2) ~2 x 1026 mol/sec => Rnuc > 0.1 km
• Activity Level vs Time has Stayed ~ Constant Over Last 3 Months
• No obvious Rotational Modulation or Outbursts to Date
• No obvious Jet Concentrations – Maybe a Sub Solar Point Enhancement?
• Qdust ~ 500 kg/sec (= 1.3 x 1010 kg total loss, Sep 2012 – Jul 2013; => Rnuc > 0.2
km for 0.35 g/cm3 density nucleus)
• Could Very Well be C/Kohoutek II, the Sequel
• Could Outburst and Fragment Inside Water, Dust Ice Lines @ rh = 2.5, 0.05 AU
About The “K” Word
Being on its first passage through the inner system may very well be the reason for
ISON's precocious activity yet small size (< 2 km radius, Li et al. 2013 CBET 3496) and
simple outgassing pattern - the comet is little evolved since its formation, and
contains relatively more highly volatile ices than a JFC or LP (few thousand year
period) comet, which are much more water rich per kg of nuclear material. Rapid
depletion of these highly volatile ices in the surface layers of the comet at
heliocentric distances of 5 to 10 AU may also be why we could be observing a
"Kohoutek-like comet”. As much as we may not want to mention this mysterious
under-performer in the night skies, C/1973 E1 (Kohoutek) was actually a bright
comet (min [V]~0) during its inner passage through the solar system and the subject
of an extensive observing campaign. A dynamically new comet discovered outside
the orbit of Jupiter (Marsden 1974), Kohoutek evinced an initally steep production
rate slope, a leveling off of production at 3 to 4 AU inbound (Delsemme 1975), and a
close passage by the Sun (q = 0.14 AU). Using the first generations of CCD optical and
IR bolometer detectors, rough estimates of Kohoutek’s nuclear size on the order of a
few km were found (A’Hearn 1975); it was measured to be highly productive in CO or
CO2 (Q(CO or CO2)/QH2O~1, Feldman et al. 1974) and in dust (Qdust,max ~ 104 kg/sec, Ney
1974, Zeilik & Wright 1975). The parallels are striking. With ISON, we thus have the
opportunity to solve a 40 yr old mystery using the latest modern detectors, while at
the same time we could be observing the most primitive of solar system objects.
Comet ISON C/2012 S1
• Discovered September 21,
2012 by Vitali Nevski and
Artyom Novichonok
• Used 0.4-m telescope at
International Scientific
Optical Network (ISON) near
Kislovodsk, Russia
• Pre-discovery image from Mt
Lemmon on Dec 28, 2011
Why is C/ISON 2012 Important (II)?
• Projected to get very bright
– Everything on its surface will sublimate near perihelion
– Allowing for many observations not commonly observable for comets
• Favorable viewing geometry for observing
– Pre-perihelion from Mars, close approach 0.07 AU C.A. =10/1/2013
– Pre-perihelion from Mercury, close approach 0.24 AU C.A.=11/18/2013
– Very Close Solar Passage, within 0.008 AU (1.7RSun) C.A.=11/28/2013
– Post-perihelion from Earth, close approach 0.42 AU, almost passing
directly above north pole C.A. = 12/26/2013
• Long lead time to perihelion
– Discovered at 6 AU, more than 1 year before perihelion
– Very long time to organize major observing campaign
• Observations planned from nearly all possible platforms in all wavelengths
(see http://sungrazer. nrl.navy.mil/index.php?p=ison)
ISON Wordle (1)
ISON Wordle (2)
Backup ISON Big Science Picture Slides
In this plot showing a 2.5 – 4.9 um EPOXI spectrum of comet C/2009 P1 (Garradd), the
narrow blue vertical bars represent the 8 BRRISON photometric imaging passbands.
Imaging of the comet by Spitzer on 13 Jun 2013 using the 10% wide IRAC 3.6 and 4.5
µm filters will help BRISSON plan its observing strategy. Ground based IRTF/SPeX 0.8 –
5.2 µm spectroscopy of the comet in October 2013 will help BRISSON perform its
continuum subtractions and color corrections, and provide an independent measure
of the comet’s flux in regions of high atmospheric transmission outside the H2O and
CO2 emission features.

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