Joseph E. Riedel

Navigation of the Deep Space 1 spacecraft at Borrelly

The navigation challenges posed by Deep Space 1s flyby of comet Borrelly were considerable due to the uncertainty in the knowledge of the comets ephemeris, as well as difficulty in determining the spacecrafts ephemeris caused by relatively large non-gravitational forces acting on the comet. The challenges were met by using a combination of radio, optical, and interferometric data types to obtain a final fly by accuracy of less than 10 km.

Configuring the Deep Impact AutoNav System for Lunar, Comet and Mars Landing

JPL’s autonomous onboard optical navigation system – AutoNav which has been responsible for obtaining all of NASA’s close-up images of comet nuclei, is being expanded in capability to accomplish a host of much more advanced missions than even the spectacular impact with comet Tempel-1 on July 4, 2005 (Figure 1). Among the most important of these mission scenarios are those that require precision landing on the Moon, a comet, and Mars. Lunar missions, in particular, are high on NASA’s agenda; both manned and unmanned. AutoNav is being utilized at this stage as a platform for evaluating lunar landing navigation strategies, and for testing algorithms, and indeed is being extended to become an onboard AutoGNC (Guidance Navigation and Control) system, that is an integrated inertial position and attitude determination function. At the core of these strategies is the nature and form of the optical navigation techniques to be used. AutoNav is being integrated with a comprehensive system for surface modeling and landmark tracking called OBIRON (OnBoard Image Registration for Optical Navigation). OBIRON provides both the means of simulation and onboard processing for purposes of estimating spacecraft position and attitude. This paper will describe the system architecture of the AutoGNC landing configuration, and also the simulation platform that provides simulated sensor inputs to the AutoGNC system. During the landing, performance of the system was excellent, with meter-level knowledge and control achieved. This paper will provide an evaluation of these results, and the associated system and process, from trial simulated operation of the system during landings at the Moon and on a small body.

AutoNav Mark3 : engineering the next generation of autonomous onboard navigation and guidance

The success of JPLs AutoNav system at comet Tempel-1 on July 4, 2005, demonstrated the power of autonomous navigation technology for the Deep Impact Mission. This software is being planned for use as the onboard navigation, tracking and rendezvous system for a Mars Sample Return Mission technology demonstration, and several mission proposals are evaluating its use for rendezvous with, and landing on asteroids. Before this however, extensive re-engineering of AutoNav will take place. This paper describes the AutoNav systems-engineering effort in several areas: extending the capabilities, improving operability, utilizing new hardware elements, and demonstrating the new possibilities of AutoNav in simulations.

The challenges of deep impact autonomous navigation

On July 4, 2005 at 05:44:34 UTC the Impactor spacecraft (s/c) impacted comet 9P/Tempel 1 with a relative speed of more than 10 km/s. The Flyby s/c captured the impact event, using both the medium resolution imager and the high resolution imager, and tracked the impact site for the entire observing period following impact. The objective of the Impactor s/c was to impact in an illuminated area viewable from the Flyby s/c and telemeter high-resolution context images of the impact site prior to impact. The Flyby s/c had two primary objectives: (1) capture the impact event in order to observe the ejecta plume expansion dynamics and (2) track the impact site for at least 800 s to observe the crater formation and capture high-resolution images of the fully developed crater. All of these objectives were met by estimating the trajectory of each spacecraft relative to 9P/Tempel 1 using the autonomous navigation system, precise attitude information from the attitude determination and control subsystem, and allowing each spacecraft to independently select the same impact site. This paper describes the challenges of targeting and tracking comet 9P/Tempel 1.

Radioisotope power system-based enceladus smallsat mission concept: Enceladus express

The coming decades of planetary science and deep space exploration will likely have a combination of more ambitious missions and ever more constrained budgets. The outer solar system, in particular, poses a challenge for lower mission cost as the principal need for a robotic craft — a source of energy — is difficult to supply through conventional means (solar energy). Even as far from the Sun as Saturn, the solar energy density is only 1% of that at Earth. Not viewed typically as a power source for low-cost missions, radioisotope power systems (RPS) may well fill that role by providing power to small spacecraft in the outer solar system. And the outer solar system beckons with extremely compelling science. The rich dynamics of the atmospheres of the gas giants are continuously operating laboratories of extreme weather processes, examples of which in miniaturized scale may become more familiar here on Earth. Enceladus, a small moon of Saturn, has been seen by the Cassini mission to be a site of continuous high geologic activity, with plumes of water vapor and particles pumped hundreds of kilometers above the surface, indeed into Saturn orbit. The internal heating mechanisms of this activity beg for explanation, and more importantly, initial measurements by the Cassini spacecraft give tantalizing clues that the geo-thermal source of the heating is, in fact, maintaining a global sub-surface ocean, which in combination could provide a habitat for life. This paper will explore how existing and currently available RPS elements may make mission concepts to explore the intriguing science of Enceladus economically tractable, and at the same time provide a generic platform for other small but highly capable spacecraft to explore the outer solar system.