A wait in excess of four years is almost over for scientists and engineers eagerly awaiting launch of the first test flight of a revolutionary solar sail. The spacecraft has been shipped from its factory to a port in far northern Russia to undergo final preparations for its submarine launch next month.

Cosmos 1 will be launched from a submarine aboard a Volna rocket. Credit: Michael Carroll, The Planetary Society

Planetary Society officials managing the Cosmos 1 mission announced the significant milestone and official target launch date on Monday.

"Reaching this milestone puts us on the doorstep to space," said Louis Friedman, Planetary Society executive director and Cosmos 1 project manager. "We are proud of our new spacecraft and hope that Cosmos 1 blazes a new path into the solar system, opening the way to eventual journeys to the stars."

Liftoff has been scheduled for the opening of a launch period on June 21 at 1946 GMT (3:46 p.m. EDT) from a Russian Navy submarine in the Barents Sea above the Arctic Circle. Its Volna rocket - a converted ballistic missile - will place the small Cosmos 1 solar sail into a suborbital trajectory where a boost module will fire to place the 90-pound craft into an 500-mile polar orbit.

The spacecraft has been under construction at the NPO Lavochkin facility in Moscow from its inception, and final vibration, thermal, and electrical tests took place earlier this year prior to its shipment to the port of Severmorsk, Russia, on the Barents Sea.

Upon its arrival, flight batteries will be installed and the pyrotechnic charges will be put in place for the deployment of the eight ultra-thin sail blades crucial to the mission. With the solar sail ready for launch, the vehicle will be mated with its orbital injection motor and shrouded within the tip of the Volna rocket.

The three-stage booster will then be loaded aboard the Russian Navy submarine about three days before liftoff for final integration, followed by the departure of the vessel to the launch zone.

An artist's concept shows the solar sail orbiting Earth. Credit: Babakin Space Center, The Planetary Society

In addition to work going on in Russia, other members of the operations teams in Moscow and Pasadena, California, will be rehearsing for different crucial aspects of the flight.

"We have to be ready for daily communications with the spacecraft and for receiving the data and images it returns from orbit," Friedman said.

Friedman wrote in an online update that he felt "pretty nervous, highly anxious, full of hope, and proud" as the moment of truth rapidly approaches. "We are poised for success."

The Cosmos 1 mission - first announced in early 2001 - has been postponed for various reasons, including the failure of two suborbital flights of its Volna launch vehicle and delays in the arrival of several critical parts. A scale model of the solar sail spacecraft flew on the Volna in 2001, followed a year later by a test of an unrelated inflatable heat shield. Neither craft was recovered.

A number of electronic components were delivered behind schedule due to testing failures, which also contributed to the large number of delays.

"We decided to launch when we are ready," Friedman wrote in an earlier update.