201 research outputs found
Forms and Rotational States of the Nuclei of Ecliptic Comets
In this thesis I present measurements of the physical properties of the
nuclei of Jupiter Family comets (JFCs), based on time-series observations. From
the time-series photometry rotation rates and elongations were measured, and
from these constraints were placed on the bulk density and porosity of nuclei.
Multi-filter imaging was performed to enable measurement of their surface
colours. In addition, a large amount of `snap-shot' imaging was performed
during the observing runs, and taken with the time-series data is used to
measure nuclei sizes. These results are compared with other data from the
literature to study the general properties of JFC nuclei.
(Abridged)Comment: Ph.D thesis, Queen's University Belfast, Sept 2006. Full text at
http://homepage.mac.com/colinsnodgrass/FileSharing2.htm
Mony a mickle maks a muckle: minor body observations with optical telescopes of all sizes
I review the current capabilities of small, medium and large telescopes in the study of minor bodies of the Solar System (MBOSS), with the goal of identifying those areas where the next generation of Extremely Large Telescopes (ELTs) are required to progress. This also leads to a discussion of the synergies between large and small telescopes. It is clear that the new facilities that will become available in the next decades will allow us to discover smaller and more distant objects (completing size distributions) and to characterise and even resolve larger individual bodies and multiple systems, however we must also recognise that there is still much to be learned from wide surveys that require more time on more telescopes than can ever be available on ELTs. Smaller telescopes are still required to discover and characterise large samples of MBOSS
Asteroid belt multiple flyby options for M-Class Missions
Addressing many of the fundamental questions in modern planetary science, as well as in ESAâs cosmic vision, requires a comprehensive knowledge of our Solar Systemâs asteroid belt. This paper investigates potential opportunities for medium-class asteroid belt survey missions in the timeframe of 2029-2030. The study has been developed in support to CASTAway Asteroid Spectroscopic Survey mission proposal, which is to be submitted to the latest ESAâs medium size mission call. CASTAway envisages the launch of a small telescope with relatively straightforward (i.e. high TRL) remote sensing instrumentation to observe asteroids at a long-range (i.e. point source), but also at a short-range, resolving them at ~10 m resolution. This paper presents a challenging multi-objective optimization problem and discusses the feasibility of such a mission concept. A baseline trajectory is presented that meets both ESAâs medium size mission constraints and the science requirements. The trajectory loops through the asteroid belt during 7 years, visiting 10 objects of a wide range of characteristics, providing sufficient survey time to obtain compositional information for 10,000s of objects and the serendipitous discovery of also 10,000s of 10-m class asteroids. The methodology developed has enabled the exploration of the entire design space for a conservative Soyuz-launch performance, and has found a total of 200 different tour opportunities of the asteroid belt; all compliant with ESAâs 5th call for medium size missions
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Penetrators as a deployment tool for Mass Spectrometer instrumentation
We discuss penetrator deployment systems and Mass Spectrometer (MS) based instrumentation that offer the potential for future characterization and understanding of the volatile content at the surface and near-surface of airless bodies in the Solar System. We review previous penetrator missions, systems and instrumentation, before considering future options to bodies such as the moon and small solar system bodies
Gemini and Lowell observations of 67P/ChuryumovâGerasimenko during the <i>Rosetta</i> mission
We present observations of comet 67P/ChuryumovâGerasimenko acquired in support of the Rosetta mission. We obtained usable data on 68 nights from 2014 September until 2016 May, with data acquired regularly whenever the comet was observable. We collected an extensive set of near-IR J, H and Ks data throughout the apparition plus visible-light images in g', r', i' and z' when the comet was fainter. We also obtained broad-band R and narrow-band CN filter observations when the comet was brightest using telescopes at Lowell Observatory. The
appearance was dominated by a central condensation and the tail until 2015 June. From 2015 August onwards, there were clear asymmetries in the coma, which enhancements revealed to be due to the presence of up to three features (i.e. jets). The features were similar in all broad-band filters; CN images did not show these features but were instead broadly enhanced in the southeastern hemisphere. Modelling using the parameters from Vincent et al. replicated the dust morphology reasonably well, indicating that the pole orientation and locations of active areas have been relatively unchanged over at least the last three apparitions. The dust production, as measured by A(0°)fÏ peaked âŒ30 d after perihelion and was consistent with
predictions from previous apparitions. A(0°)fÏ as a function of heliocentric distance was well fitted by a power law with slope â4.2 from 35 to 120 d post-perihelion. We detected photometric evidence of apparent outbursts on 2015 August 22 and 2015 September 19, although neither was discernible morphologically in this data set
A Potential Aid in the Target Selection for the Comet Interceptor Mission
The upcoming Comet Interceptor mission involves a parking phase around the
Sun-Earth L2 point before transferring to intercept the orbit of a long period
comet, interstellar object or a back-up target in the form of a short-period
comet. The target is not certain to be known before the launch in 2029. During
the parking phase there may thus arise a scenario wherein a decision needs to
be taken of whether to go for a particular comet or whether to discard that
option in the hope that a better target will appear within a reasonable time
frame later on. We present an expectation value-based formalism that could aid
in the associated decision making provided that outlined requirements for its
implementation exist.Comment: Accepted for publication in Planetary and Space Scienc
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 âOumuamua
During the formation and evolution of the Solar System, significant numbers of cometary and asteroidal bodies were ejected into interstellar space. It is reasonable to expect that the same happened for planetary systems other than our own. Detection of such interstellar objects would allow us to probe the planetesimal formation processes around other stars, possibly together with the effects of long-term exposure to the interstellar medium. 1I/2017 U1 âOumuamua is the first known interstellar object, discovered by the Pan-STARRS1 telescope in October 2017. The discovery epoch photometry implies a highly elongated body with radii of ~â200âĂâ20âm when a comet-like geometric albedo of 0.04 is assumed. The observable interstellar object population is expected to be dominated by comet-like bodies in agreement with our spectra, yet the reported inactivity of 'Oumuamua implies a lack of surface ice. Here, we report spectroscopic characterization of âOumuamua, finding it to be variable with time but similar to organically rich surfaces found in the outer Solar System. We show that this is consistent with predictions of an insulating mantle produced by long-term cosmic ray exposure. An internal icy composition cannot therefore be ruled out by the lack of activity, even though âOumuamua passed within 0.25âau of the Sun
The dust environment of comet 67P/ChuryumovâGerasimenko: results from Monte Carlo dust tail modelling applied to a large ground-based observation data set
We present an extensive data set of ground-based observations and models of the dust environment of comet 67P/ChuryumovâGerasimenko covering a large portion of the orbital arc from about 4.5 au pre-perihelion through 3.0 au post-perihelion, acquired during the current orbit. In addition, we have also applied the model to a dust trail image acquired during this orbit, as well as to dust trail observations obtained during previous orbits, in both the visible and the infrared. The results of the Monte Carlo modelling of the dust tail and trail data are generally consistent with the in situ results reported so far by the Rosetta instruments Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) and Grain Impact Analyser and Dust
Accumulator (GIADA). We found the comet nucleus already active at 4.5 au pre-perihelion, with a dust production rate increasing up to âŒ3000 kg sâ1 some 20 d after perihelion passage. The dust size distribution at sizes smaller than r = 1 mm is linked to the nucleus seasons, being described by a power law of index â3.0 during the comet nucleus southern hemisphere winter but becoming considerably steeper, with values between â3.6 and â4.3, during the nucleus southern hemisphere summer, which includes perihelion passage (from about 1.7 au inbound to 2.4 au outbound). This agrees with the increase of the steepness of the dust size distribution found from GIADA measurements at perihelion showing a power index of â3.7. The size distribution at sizes larger than 1 mm for the current orbit is set to a power law of index â3.6, which is near the average value of in situ measurements by OSIRIS on large particles. However, in order to fit the trail data acquired during past orbits previous to the 2009 perihelion passage, a steeper power-law index of â4.1 has been set at those dates, in agreement with previous trail modelling. The particle sizes are set at a minimum of r = 10 ÎŒm, and a maximum size, which increases with decreasing heliocentric distance, in the 1â40 cm radius domain. The particle terminal velocities are found to be consistent with the in situ measurements as derived from the instrument GIADA on board Rosetta
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