(CNN) -- An engine fired to push NASA's next Mars mission into orbit around the red planet Thursday, but engineers failed to receive digital signals that all went well and have since lost contact with the spacecraft.

Following a 286-day journey, the Mars Climate Orbiter engine ignited as expected at 5:01 EDT. A signal was expected about 25 minutes later when the satellite cruised out from behind the planet, but engineers heard nothing. "We're in a state where we're not quite sure what's happened," said Richard Cook, project manager for NASA's Mars Surveyor program, which includes Climate Orbiter.  "At this point, we're still very confident that we're in orbit in Mars and that we're going to see the spacecraft signal in a few hours."

Initial data showed some unexpected results, said project manager John McNaimee. "The spacecraft was entering its corridor somewhat low," he said.  "The result of that could be an orbit that is significantly different than the one planned," he said. Engineers worked to recalculate the spacecraft's location so they could repoint gigantic radio antennae on Earth to receive signals from Climate Orbiter.

Project scientist Richard Zurek likened the effort of searching for the spacecraft to "looking for a signal in the cosmic haystack."

 "Until we establish contact, we're really not going to have any idea of where the spacecraft was and how deep into the atmosphere it went," he said. An unplanned, steep entry into the atmosphere could have damaged Climate Orbiter.