The Stardust-NExT utilized the existing spacecraft to flyby comet Tempel 1 and observe changes since NASA’s Deep Impact mission visited it in 2005. Stardust-NExT will provide NASA with a first-time opportunity to compare observations of a single comet made at close range during two successive perihelion passages, at low risk and low cost.
In 2005, Tempel 1 made its closest approach to the sun, possibly changing the surface of the comet. With a 3-year trajectory, the mission flight plan is designed in a similar way to that of the original mission, with an Earth gravity assist (EGA) in 2009 to achieve the flyby of Tempel 1 in 2011. The original flight path of the Stardust spacecraft to Wild 2 included an EGA in 2001.
Mission Design and Navigation:
The Stardust spacecraft divert maneuver that followed the release of the sample return capsule (SRC) was intentionally designed to place the spacecraft in a trajectory that returns to Earth in case the SRC release that occurred January 15 had failed. Thus the current orbit intrinsically provides the Earth gravity-assist (EGA) flyby opportunity in 2009, which enables the Tempel 1 encounter. The mission duration, from the divert maneuver after SRC release (January 15, 2006) to the February 14, 2011 Tempel 1 encounter, is a little over 5 years. The date of encounter will be optimized during the mission to account for improved knowledge of the comet’s ephemeris during cruise, and to maximize the probability of viewing the Deep Impact impact crater. Table F-1 summarizes the principal characteristics of the comet encounter.
|Table F-1. Tempel 1 Encounter Characteristics|
|Flyby date||February 14, 2011|
|Approach Phase angle||81.6°|
|Closest Approach Point||200 km altitude, 40° south of direction to the Sun|
|Solar Distance||1.55 AU|
|Earth Distance||2.25 AU|
The trajectory consists of four loops of the sun in two separate orbits. Loops 1 and 2 represent the orbit the spacecraft bus was left in after the sample return on January 15, 2006. The EGA on January 14, 2009 places the spacecraft in the final heliocentric orbit (Loops 3 and 4) intercepting Tempel 1 on February 14, 2011 (39d after the comet’s perihelion). This profile is very similar to the launch-to-Wild 2 phase of the Stardust primary mission.
|Figure F-1. Stardust-NExT trajectory, with one EGA prior to Tempel 1 encounter, provides for an uncomplicated mission simpler than the Stardust prime mission.|