America's invasion of Grenada in the fall of 1983 was a botched operation from the word go, and should never have gotten to the word go in the first place -- or so says a report on public TV's "Frontline" series tonight.

Although it is not used on the broadcast itself, the phrase "colossal hoax" comes to mind. This isn't the first time that's been suggested with regard to Grenada, but here the incriminating details coalesce to form a portrait in delusionary incompetence.

"Operation Urgent Fury," reported by investigative journalist Seymour M. Hersh and airing at 9 on Channel 26, concludes that the invasion of the Caribbean island involved "a dismal failure by American intelligence agencies" and was a mercy mission that "in the end, jeopardized the very lives it was meant to save."

The lives were those of 595 U.S. medical students attending college on the island. Hersh and his witnesses suggest they were in less danger before the U.S. rescue than they were once it began, since ragged intelligence work had failed to provide adequate data on the students' whereabouts as well as on the extent of antiaircraft resistance that invading forces would be meeting.

A Marine involved in the operation recalls that when he and his fellow soldiers landed on the island they were provided not with grid coordinates indicating where to direct their fire, but with tourist maps highlighting "points of interest," such as a nutmeg farm.

Hersh does not disprove the Reagan administration's contention that the new government of Grenada posed a threat to U.S. security, although he tries. But as for the invasion itself having been a sloppy-boppy Keystone Kop production, the assembled authorities and participants make a persuasive case.

Military watchdog William Lind, who is critical of the 82nd Airborne's record on the island, says the unit managed to advance only five kilometers in three days -- and this against "absolute bottom-of-the-barrel opposition ... a fourth- or fifth-rate opponent.

"People say, well, we did well because we won," Lind notes, "but the New York City police department could have won in Grenada."

Lt. Gen. Norman Schwartzkopf, describing one of the innumerable snafus, begins a recollection by saying, "If it had been a Hollywood movie ..." That may have been just what it was, at least in a movie-star president's mind. When Clint Eastwood tried making it the climax of an actual Hollywood movie, "Heartbreak Ridge," the public shrugged; it had already been on TV.

Ronald Reagan went on TV during the invasion to assure us all that our borders were safe and the medical students were too, but at least 100 still had not been rescued at that point, the report says. Reagan convinced the country, however, and perhaps himself, that this was a military triumph, and he used it to justify the rallying cry "America is back."

"Operation Urgent Fury" was produced for "Frontline" by Mark Obenhaus. It is pretty much a succession of talking heads -- among them, Sen. Sam Nunn (D-Ga.), chairman of the Armed Services Committee, and former ambassador to Barbados Sally Shelton -- but the heads have something to say.

It would all be quite funny if it weren't also quite sad.