the unprecedented rosetta mission to comet 67p/churyumov–gerasimenko
DESCRIPTION
After almost 11 years in transit and 4 gravitational assists from the Earth and Mars, the European Space Agency’s Rosetta probe has arrived at the Jupiter-family comet 67P/Churyumov–Gerasimenko. Arriving on Wednesday, August 6th, the probe went into a 100 km-high orbit around the comet, both of which are now in common orbit around the sun. Depending on the comet’s activity, Rosetta will come as close as 10 km to the comet’s nucleus over the course of the mission. With a high orbital eccentricity (the orbit’s deviation from a perfect circle) of 0.640, a perihelion of 1.2 AU and an aphelion of 5.68 AU, 67P/Churyumov–Gerasimenko is now in common orbit around the sun with Rosetta. Rosetta is a cornerstone mission of the European Space Agency (ESA). It is an unprecedented landmark achievement in human history and the history of science. Humankind has placed a sophisticated instrument of science in orbit around a comet's nucleus and has placed a robotic lander in the surface of that nucleus! Rosetta will chase down, go into orbit around, and land on the object of interest. It will study 67P/Churyumov-Gerasimenko with a combination of remote sensing and in situ measurements. The mission has 2 phases, the ongoing orbital phase and the landing phase. During the ongoing orbital phase, the spacecraft will examine the comet up close with its suite of 11 instruments. During the landing phase, the orbiter will release the Philae lander which carries an onboard suite of 10 instruments for imaging and sampling the comet’s nucleus. The mission will track the comet through perihelion, its closest approach to the sun, examining its behavior before, during and after. Providing an introductory retrospective of comets, sometimes regarded as harbingers of doom, Prof. Madigan discusses this historic mission, a mission that includes study of the comet from the surface of its nucleus! This public event was hosted at the Ross School (East Hampton, NY) by the Montauk Observatory on September 18th, 2014.TRANSCRIPT
The Unprecedented Rosetta Mission to Comet 67P/Churyumov–Gerasimenko
Prof. Thomas Madigan
Overview• Historical retrospective of comets• The Dawn of the Modern Era and a New
Intellectual Renaissance• Our Modern Understanding of Comets• Why study comets?• The Importance of visiting Comet 67P/C-G–Why this comet?
• The 67P/C-G Mission
Since antiquity comets were thought of as harbingers of doom. The word “disaster” is derived from the Greek word meaning “bad star” and was often used to refer to the appearance of a comet within the context of a certain calamity
dis·as·ter
Origin• late 16th century: from Italian disastro ‘ill-
starred event,’ from dis- (expressing negation) + astro ‘star’ (from Latin astrum ).
Antiquity
The Greeks– Some suggest that comets are solar system
objects like planets– Others suggest that they were burning clouds or
optical phenomena in the Earth’s atmosphere– Aristotle (400 BC), a Geocentrist, adopts this later
view, suggesting that comets are "windy exhalations“ from the Earth
The 1066 apparition of Halley's Comet occurred during the Battle of Hastings and is represented in the Bayeux Tapestry (scenes 32-33). Credit: By Myrabella
• Apparition of Comet 44 BC– Death of Julius Ceasar
• 1910 apparition of Halley’s Cometthe Earth passed through the comet's tail and erroneous newspaper reports inspired a fear that cyanogen in the tail might poison millions
• Comet Hale–Bopp in 1997triggered the mass suicide of the Heaven's Gate cult
The Beginnings of Modernityand the Scientific Revolution
(The Dawn of Reason)
CopernicusPublishes De Revolutionibus Orbium Coelestium (On the Revolutions of the Celestial Spheres) just before his death in 1543, proposing a Heliocentric model of the solar systemIs renowned as the “Father of Modern Astronomy” for rekindling this idea, for proposing a model “More Pleasing to the Mind”
– Meticulous observations of the planets at
Uraniburg on the island of Hven (Denmark)– Proposes the use of careful experiments rather
than lengthy philosophical debates– computes the distance to the Great Comet of
1577 using the parallax method– Subsequently proposes a hybrid model that
includes aspects of the Geocentric and Heliocentric models
Tycho Brahe
The path of the comet Tycho Brahe saw in 1577, in his hybrid geo/heliocentric model.
Kepler publishes Astronomia Nova
Kepler’s 3 Laws1) All Orbits are Elliptical
2) Equal areas are swept out in equal times
The Copernican Revolution
3P A
3) The squares of the periods of the planets are proportional to the cubes of their semi-major axes: P2 = A3 . Thus Example: Distance to Saturn (Saturn’s SMA) = 9.5 AU
Said differently, the period varies as the 3/2 power of the semi-major axis
To find the semi-major axis, A, in terms of the period
Example: Period of Comet 67P/C-G = 6.45 yrs
3 2A P
3P A
39.5 857.375 29.3 yrsP
3 2 36.45 41.54 3.46 U AA
Galileo
Uses the Scientific Method and extensive use of the telescope as an instrument of science to demonstrate the veracity of the Copernican model
Renowned as the Father of Modern Science
Isaac Newton
• Develops Classical Mechanics and Laws of Motion• Develops The Law of Universal Gravitation• Publishes Principia Mathematica• Along with Liebnitz, develops Calculus• Renowned as one of the most influential scientists of
all time and a key figure in the scientific revolution
Today, we know comets are left over debris from the formation of the solar system, most of which originate in the Oort cloud, a vast spherical halo beginning at about 250 times Pluto’s distance from the sun
Our Modern Understanding of Comets
Comets have a wide range of orbital periods and orbital eccentricities. Short period comets originate in the Kuiper belt, a debris disk beyond the orbit of Neptune and Pluto. The longer period comets originate in the Oort cloud.
Our Modern Understanding of Comets
Why Study Comets?
Why Study Comets?Comets are composed of material unadulterated since the formation of the solar system
What is the true nature of a comet?Does it always present with a beautiful tail or is it something quite different?
Lets take a look
And
Comet 67P/C-G
How do comets compare to other objects?
Cities 4 – 8 KM?Oceans 3,000 KM?Planets 10,000 KM?Stars (the sun) 700,000 KM (radius)?
3.5 km
4 km
The Nucleus is the loosely bound agglomeration of debris held together by ice of various compositions. This is the “dormant” state of the comet
This material “activates” as the comet approaches the sun and begins to warm. This process forms the “Coma”
What happens to a comet as it approaches the sun?
Lets take a look
A Tail Forms!
Why does the tail form and what is it comprised of?
Why does the tail form and what is it comprised of?– As the comet approaches the sun, the nucleus
begins to warm and the ice starts to sublimate (evaporate)
Why does the tail form and what is it comprised of?– As the comet approaches the sun, the nucleus
begins to warm and the ice starts to sublimate (evaporate)
– At about 1 AU from the sun, the tail forms, pushed out by Solar Wind and Radiation Pressure
Why does the tail form and what is it comprised of?– As the comet approaches the sun, the nucleus
begins to warm and the ice starts to sublimate (evaporate)
– At about 1 AU from the sun, the tail forms, pushed out by Solar Wind and Radiation Pressure
– Solar radiation pressure forms a dust tail
Why does the tail form and what is it comprised of?– As the comet approaches the sun, the nucleus
begins to warm and the ice starts to sublimate (evaporate)
– At about 1 AU from the sun, the tail forms, pushed out by Solar Wind and Radiation Pressure
– Solar radiation pressure forms a dust tail– Solar Ultraviolet radiation forms a gas-ion tail
Why does the tail form and what is it comprised of?– As the comet approaches the sun, the nucleus
begins to warm and the ice starts to sublimate (evaporate)
– At about 1 AU from the sun, the tail forms, pushed out by Solar Wind and Radiation Pressure
– Solar radiation pressure forms a dust tail– Solar Ultraviolet radiation forms a gas-ion tail– The Solar wind pushes the gas-ion tail in the
opposite direction
Why does the tail form and what is it comprised of?– As the comet approaches the sun, the nucleus
begins to warm and the ice starts to sublimate (evaporate)
– At about 1 AU from the sun, the tail forms, pushed out by Solar Wind and Radiation Pressure
– Solar radiation pressure forms a dust tail– Solar Ultraviolet radiation forms a gas-ion tail– The Solar wind pushes the gas-ion tail in the
opposite direction– The gas-ion tail follows the magnetic field lines
Comet McNaught prior to Perihelion, 10 January, 2007
What happens next?
The comet passes around the sun at Perihelionor
The comet becomes a “Sun-grazing” comet
Comet McNaught after Perihelion, 20 January, 2007!
Comet McNaught after Perihelion, 20 January, 2007!
Why Comet 67P/C-G
Why Comet 67P/C-G
• Long standing desire to rendezvous with a comet
Why Comet 67P/C-G
• Long standing desire to rendezvous with a comet
• Target of opportunity
The 67P/C-G Mission
The 67P/C-G Mission
• Launched on 2 March, 2004
The 67P/C-G Mission
The 67P/C-G Mission
• Launched on 2 March, 2004• Gravity assists and various maneuvers
The 67P/C-G Mission
• Launched on 2 March, 2004• Gravity assists and various manuvers• Enter deep space hibernation 8 June, 2011
The 67P/C-G Mission
• Launched on 2 March, 2004• Gravity assists and various manuvers• Enter deep space hibernation 8 June, 2011• Exit deep space hibernation 20, January 2014
The 67P/C-G Mission
• Launched on 2 March, 2004• Gravity assists and various manuvers• Enter deep space hibernation 8 June, 2011• Exit deep space hibernation 20, January 2014• 6 August, 2014– Rendezvous with 67P/C-G on, approaching to
within 100 km, reducing its velocity to 1 m/sec
The 67P/C-G Mission
• Launched on 2 March, 2004• 6 August, 2014– Rendezvous with 67P/C-G on, approaching to within
100 km, reducing its velocity to 1 m/sec– Commences comet mapping and characterization to
determine a stable orbit and viable landing location for Philae lander
• 10 September 2014– Rosetta enters the Global Mapping Phase, orbiting
67/C-G at an altitude of 29 km
The 67P/C-G Mission
• Launched on 2 March, 2004• 6 August, 2014
– Rendezvous with 67P/C-G on, approaching to within 100 km, reducing its velocity to 1 m/sec
– Commences comet mapping and characterization to determine a stable orbit and viable landing location for Philae lander
• 10 September 2014– Rosetta enters the Global Mapping Phase, orbiting 67/C-G at an
altitude of 29 km• 15 September, 2014
– "Site J" on the "head" of the comet selected as the landing site for Philae
The Rosetta orbiter carries an instrument suite of 11 science instrument packages
The Rosetta orbiter
Philae, The Rosetta Lander
The Philae lander carries 10 science instrument packages
The importance of ground-based observations of Comet 67P/C-G with the VLT
The 67P/C-G Mission
The importance of ground-based observations of Comet 67P/C-G with the VLT– Rosetta is operating in the comet’s coma!
The 67P/C-G Mission
Why did it take 12 years?
Why did it take 12 years?– The required rendezvous velocity was 16 km/sec
Why did it take 12 years?– The required rendezvous velocity was 16 km/sec– The average cruise velocity of Rosetta was 20
km/sec
Why did it take 12 years?– The required rendezvous velocity was 16 km/sec– The average cruise velocity of Rosetta was 20
km/sec– At times, the comet was traveling at 34 km/sec in its
orbit
Why did it take 12 years?– The required rendezvous velocity was 16 km/sec– The average cruise velocity of Rosetta was 20
km/sec– At times, the comet was traveling at 34 km/sec in its
orbit– To negotiate the complex trajectory necessary to
intercept the comet, Rosetta needed 3 gravity assists from Earth and one from Mars
Where is Rosetta Today?http://sci.esa.int/where_is_rosetta
