Showing papers on "Trojan published in 1999"

Cartography for Martian Trojans

Abstract: The last few months have seen the discovery of a second Martian Trojan (1998 VF31) as well as two further possible candidates (1998 QH56 and 1998 SD4). Together with the previously discovered Martian satellite 5261 Eureka, these are the only known possible solar system Trojan asteroids not associated with Jupiter. Here maps of the locations of the stable Trojan trajectories of Mars are presented. These are constructed by integrating an ensemble of in-plane and inclined orbits in the vicinity of the Martian Lagrangian points for between 25 and 60 million years. The survivors occupy a band of inclinations between 15° and 40° and longitudes between 240° and 330° at the L5 Lagrangian point. Around the L4 point, stable Trojans inhabit two bands of inclinations (15° < i < 30° and 32° < i < 40°) with longitudes restricted between 25° and 120°. Both 5261 Eureka and 1998 VF31 lie deep within one of the stable zones, which suggests that they may be of primordial origin. Around Mars, the number of such undiscovered primordial objects with sizes greater than 1 km may be as high as ~50. The two candidates 1998 QH56 and 1998 SD4 are not presently on Trojan orbits and will enter the sphere of influence of Mars within half a million years.

Cartography for Martian Trojans

Abstract: The last few months have seen the discovery of a second Martian Trojan (1998 VF31), as well as two further possible candidates (1998 QH56 and 1998 SD4). Together with the previously discovered Martian satellite 5261 Eureka, these are the only known possible solar system Trojan asteroids not associated with Jupiter. Here, maps of the locations of the stable Trojan trajectories of Mars are presented. These are constructed by integrating an ensemble of in-plane and inclined orbits in the vicinity of the Martian Lagrange points for between 25 million and 60 million years. The survivors occupy a band of inclinations between 15 degrees and 40 degrees and longitudes between 240 degrees and 330 degrees at the L5 Lagrange point. Around the L4 point, stable Trojans inhabit two bands of inclinations (15 degrees < i < 30 degrees and 32 degrees < i < 40 degrees) with longitudes restricted between 25 degrees and 120 degrees. Both 5261 Eureka and 1998 VF31 lie deep within one of the stable zones, which suggests they may be of primordial origin. Around Mars, the number of such undiscovered primordial objects with sizes greater than 1 km may be as high as 50. The two candidates 1998 QH56 and 1998 SD4 are not presently on Trojan orbits and will enter the sphere of influence of Mars within half a million years.

A secular theory for Trojan-type motion

Abstract: We derive a secular theory for Trojan-type motion in the framework of the restricted three-body problem, which is valid inside the entire regular coorbital region. We show that under certain conditions it is possible to extend the theory to include the secular perturbations from additional bodies and an oblate central mass. We are then able to predict the location of linear secular resonances which may play an important role in determining the long-term stability of Trojan orbits associated with planets or satellites.

Trojans in Stable Chaotic Motion

Abstract: The orbits of 13 Trojan asteroids have been calculated numerically in the model of the outer solar system for a time interval of 100 million years For these asteroids (1997) determined Lyapunov times less than 100000 years and introduced the notion “asteroids in stable chaotic motion” We studied the dynamical behavior of these Trojan asteroids (except the asteroid Thersites which escaped after 26 million years) within 11 time intervals — ie subintervals of the whole time — by means of: (1) a numerical frequency analysis (2) the root mean square (rms) of the orbital elements and (3) the proper elements For each time interval we compared the root mean squares of the orbital elements (a, e and i) with the corresponding proper element It turned out that the variations of the proper elements e p in the different time intervals are correlated with the corresponding rms(e); this is not the case for sin I p with rms(i)

GuardHouse: Locking the Stable door ahead of the Trojan Horse

Abstract: Once attackers have penetrated a system, they will usually take advantage of their position by extending their reach to compromise other systems (e.g., by sniffing passwords from the network), and by installing "back doors" that will enable them to regain access even if the original insecurity is repaired. A common approach is to install a modified version of a standard system daemon such as telnetd. It is also common for attackers to attempt to cover their tracks by installing doctored versions of standard programs like ls, ps and sum. Programs like this, which conceal something harmful inside a harmless looking exterior, are called Trojan Horses. GuardHouse detects Trojan Horses as they are about to be activated. It is similar in its goals to Kim and Spafford''s Tripwire, but detects intrusions with lower latency. That is, rather than laying dormant until the system administrator next runs a Tripwire integrity check, GuardHouse would detect a Trojan Horse as soon as it is run. Another difference is that GuardHouse can be configured to prevent the Trojan Horse from running at all. The paper makes three contributions. First, we show that the implementation of binary code certification in a modular system like Linux is simple. Second, we discuss configurations that trade different degrees of security for different degrees of inconvenience, but in all cases we are able to find reasonable points of compromise. Finally, we show that the impact of the additional checks on system performance is small enough to encourage the wide adoption of this technology.

Proper Elements and Stability of the Trojan Asteroids

Abstract: Up to now ∼ 400 asteroids are known which move close to the Lagrangian equilibrium points L 4 (246) and L 5 (167) of Jupiter. In this investigation the orbits of all known Trojans were integrated numerically for 10 million years using the Lie Series integrator with adaptive stepsize (Hanslmeier and Dvorak, 1984) in the dynamical model of the outer planetary system. The goal of the study was to extend the computation of the proper elements for all known Trojans for a longer time interval; the respective results are compared to already existing ones (e.g. Bien & Schubart, 1987; Milani, 1993).

Trojan : A High-Performance Simulator for Shared Memory Architectures

Abstract: The paper presents an execution driven simulator called Trojan, which is an extended version of MIT Proteus, for evaluating the performance of parallel shared memory machines. The key features of Trojan are: (1) it simulates efficiently both process model based (e.g., SPLASH) and thread model based applications (e.g., SPLASH2) (a \"copy on write\" mechanism is used on process based applications implemented on a threads package); (2) it provides support for virtual memory simulation, which is, to our knowledge, the first execution driven simulator to offer this functionality; and (3) Trojan does not require making any modification to applications, which results in increased accuracy and usability. We have used Trojan extensively to study cache behavior, network traffic patterns, multiprocessor architectures, and application behavior.