Europe's Ariane 5 rocket. Credit: ESA/CNES/ARIANESPACE-S. Corvaja

The problems experienced by the Ariane 5 rocket program since its failure last year have impacted a pair of European science missions -- one to explore a comet, the other to orbit our moon -- that were due to launch in the first half of 2003.

After an upgraded version of the Ariane 5 called the ECA crashed into the Atlantic Ocean minutes after blasting off from Kourou, French Guiana, December 11, Arianespace and European aerospace teams launched an investigation into the mishap that destroyed two communications satellites, as well as a review of the Ariane 5 program as a whole.

Results indicated that a cooling system leak on the first stage's Vulcain 2 main engine nozzle caused the botched launch and officials ordered not only an intensive redesign of portions of the powerplant, but also an exhaustive evaluation of the Vulcain 1 used on the Ariane 5 basic version -- the Ariane 5G.

These tests and redesign activities have pushed the return to flight of the Ariane 5G until early April, while the Ariane 5 ECA isn't expected to launch before 2004 on a demonstration mission with no commercial payload aboard.

"We did a complete re-analysis of all aspects of the (Ariane) 5G, including a review of the margins on the Vulcain 1 engine and nozzle," said Arianespace spokeswoman Suzy Chambers. "To date, no improvements or adjustments have been required."

An ESA technology and science mission is facing an onslaught of delays stemming from the Ariane 5 troubles. The SMART-1 lunar orbiter was set to start its complex journey to the Moon this month, but has slipped to at least July, and potentially further.

An artist's concept of SMART-1 sailing away from Earth. Credit: ESA

The first mission in ESA's Small Missions for Advanced Research in Technology, SMART-1 is the program's flagship mission. The spacecraft will accompany a pair of communications satellites into geostationary transfer orbit, then will separate from the Ariane 5 upper stage, SMART-1 project manager Giuseppe Racca told Spaceflight Now.

The launch will feature the first use of a new configuration, or stack, of the payloads and associated hardware inside the Ariane 5's payload fairing. SMART-1 will be attached directly atop the vehicle equipment bay and the upper stage, and a payload adapter and another satellite payload will be attached above SMART-1. The Sylda 5 payload module will then be placed around the two payloads, and the other primary payload will be bolted atop the Sylda 5.

SMART-1's cutting edge ion engine will gradually pulse almost continuously beginning after about its 10th Earth orbit for about two months, gaining altitude slowly before the Moon's weaker gravitational field begins to influence the 814-pound craft's trajectory. Eventually, the lunar gravity will capture SMART-1 after over a year, then the satellite will slowly be lowered to its operational orbit.

Objectives of SMART-1 include the testing of a number of technologies for future application to other space missions. These comprise the revolutionary solar electric and xenon gas ion propulsion system used on previous NASA missions such as Deep Space 1, as well as a suite of other technology experiments in communications and telecommand.

Scientific instruments on SMART-1 will image the lunar surface and conduct thorough studies of the components of the soils and materials on the Moon using spectroscopic analysis during at least six months in lunar orbit.

With Ariane 5 delays, Racca said the earliest SMART-1 could launch now is July 15. Arianespace notified the team of a month-long launch period beginning in mid-July and extending into August aboard an Ariane 5 with a pair of other payloads, Racca said.

One of the unique aspects of SMART-1 is that it has the ability to launch at any time and is not constrained by launch windows, time of day, or time of year.

An artist's concept of SMART-1 and its destination -- our moon. Credit: ESA

Racca said the project never looked away from the Ariane 5. "We did not really put in doubt the Ariane 5 baseline for SMART-1, despite the launcher difficulties," he said in response to written questions.

"In principle we don't need Ariane 5 as a launch vehicle, we are so small that we could actually be accommodated on many other launchers. In practice, however, switching launcher(s) at this stage would require (us) to perform a number of verification and possibly small modifications, which even though substantially limited, would affect the schedule and the cost quite severely. I think we could consider that only in (the) case of further failures or inability to launch by Arianespace."

When project engineers and officials got word of the launch delay, "the first reaction of the team was a sense of frustration," said Racca. "We had been working in the last six months almost day and night including nearly all weekends, to prepare the spacecraft for the planned launch of March 2003. However after the first reaction, we realized that some more time to finish up testing wasn't bad and we will even have some time for holidays before the hard days of the launch will come. Of course, the matter would change considerably if more delays will come, but we hope not and...we keep (our) fingers crossed."

"All in all, we are quite happy with a launch date in July, as we will have the spacecraft completely and thoroughly tested and the whole team will be fresher for the first flight operations."

In Europe, Racca reported manufacturing and testing teams continue working on the SMART-1 spacecraft at its state-of-the-art clean room. The craft is completely assembled with its propulsion and instrument packaged attached, and testing is nearing completion. Transportation to the launch site at the Guiana Space Center in Kourou, French Guiana, is expected in the early part of June.

Meanwhile, European Space Agency and Arianespace managers came to the consensus in mid-January that ESA's ambitious Rosetta comet probe would not be able to launch by the end of its required science window at the end of January to reach its target comet Wirtanen. Officials then began looking into using an alternate route of gravity assist maneuvers with planets to reach other potential comets of interest. Rosetta was originally scheduled to launch on an Ariane 5G, but it was to be the first use of a more complicated mission profile that involves multiple burns of the rocket's upper stage.

Planners immediately began working on other mission scenarios that would likely utilize either the Ariane 5 or Russian Proton vehicles to set the spacecraft on a course to intercept a variety of targets that meet both design criteria and the demands of the scientific community.

"During the decade it has taken us to develop and build Rosetta, we have faced many challenges and overcome them all. This new challenge will be met with the same energy, enthusiasm and, ultimately, success," said Rosetta project scientist Gerhard Schwehm in January shortly after the Rosetta postponement was announced.

An artist's concept of the Rosetta orbiter and its lander on the surface of a comet. Credit: Astrium/Erik Viktor

Nine concepts were studied intently, then three were selected for further analysis. These three mission plans are under strict funding guidelines that must also be taken into account. Two of the three scenarios would see launches in February 2004 or 2005 to reach comet Churyumov-Gerasimenko, and the third would see a launch toward the original target Wirtanen in January 2004.

Challenges associated with the new plans include a vastly different profile for planetary fly-bys to gain a gravity assist, or boost, toward its objective comet. Also, if Churyumov-Gerasimenko is selected, Rosetta's lander may have to be re-programmed with software to handle the increased mass and gravity field over that of Wirtanen.

Although the Ariane 5 continues to bet described as the primary launcher for Rosetta, a status report issued Thursday said ESA is "assessing launch requirements for various mission scenarios." The Proton booster received mention as a possible backup option.

The statement also said the final decision on a future course of action for Rosetta would be decided upon during the ESA science committee's scheduled meeting in May.