On Valentine's Day, as the world was celebrating the message of love, a NASA spacecraft reached the point of closest contact with a comet calculated to be half the size of Manhattan.

The periodic comet, Tempel 1, was discovered by German astronomer Ernst Wilhelm Leberecht Tempel in 1867. In every 5.5 years, the comet completes one orbit around the Sun with its orbital paths lying in between the orbits of Mars and Jupiter.

Tempel 1 was previously visited by NASA's Deep Impact spacecraft on July 4, 2005. The current fly-by of the comet by NASA's Stardust spacecraft is the first time that a comet has been re-visited to look for changes on its surface.

During the encounter phase, the spacecraft will carry out many important milestones which include turning the spacecraft to point its protective shields between it and the anticipated direction from which cometary particles would approach. Another important milestone includes scientific imaging of the comet's nucleus.

Along with the high resolution imaging of the comet's surface, Stardust-NExT mission will also measure the composition, size distribution and flux of dust emitted into the coma.

The aim is to extend knowledge of the processes that affect comet surfaces and obtain additional information on the internal structure of comet nuclei, and provide important new information on how Jupiter-family comets evolve and how they formed 4.6 billion years ago.

At the time of closest encounter, the spacecraft was approximately 200 kilometers (124 miles) from the comet's nucleus.