Today's the Big Day at Channel 9 as ownership of the station officially passes from the Evening News Association to Gannett, which purchased ENA last year . . .

Station sources expect it will be a get-acquainted sort of first day as everybody meets the visiting Gannett broadcasting division executives but no First Day Surprises . . .

You can be pretty sure somebody at Nine will pull out the early Nielsen numbers from the first two weeks of the February ratings sweeps for the edification of the new bosses . . .

They show Nine's noon news audiences outnumbering Seven's news viewers by almost 2 to 1 while swamping "Here's Lucy" on Four by more than 3 to 1 . . .

Mondays through Fridays, at both 5 and 6 p.m., Nine news leads Four and Seven by healthy margins . . . although "ABC World News Tonight" picks up a little at 6:30 in Seven's revised lineup . . .

Five's "Three's Company" finishes ahead of "CBS Evening News With Dan Rather" on Nine at 7, while "NBC Nightly News" on Four and "Jeopardy!" on Seven trail . . .

At 11 p.m., Nine's "Eyewitness News" is again dominant, followed by Four and Seven, in that order . . . all pretty much the same pattern of the January Nielsen figures . . .

ABC News has announced some changes at its Washington bureau . . .

Pentagon correspondent Dean Reynolds has been assigned to the London bureau; White House correspondent Steve Shepard goes to the Pentagon; Dennis Troute moves from the Pentagon to the Justice Department beat; and Kenneth Walker goes to the White House from Justice . . .

Also moving: the Washington headquarters of the Radio-Television News Directors Association (RTNDA) from its current digs at 1735 DeSales St. NW to Suite 615, 1717 K St. NW . . . as of April 1 . . .

RTNDA will also have a new phone number when it moves: 659-6510. That's 659-6510 . . .

ABC News reports that Ronald Perelman, chairman and chief executive officer of Pantry Pride Inc. (which recently took over Revlon), saw a segment on "World News Tonight" Sunday that detailed the financial problems of Debi Thomas, the Stanford premed student who won the senior women's title at the National Figure Skating Championships on Feb. 8 . . .

Perelman, expressing interest in helping the 18-year-old with her $30,000 annual expenses for skating lessons and freshman studies, called Sam Fine, the weekend producer of the news show in New York. Sam promised to put him in touch with Debi this week . . .

Easily the best new entry on the network scene since the first of the year is ABC's Disney Sunday Movie, which may take a bite out of "60 Minutes" yet as families discover its charms . . .

This weekend the series will tell the story of Linn Yann, the little Cambodian girl whose family made it all the way from a refugee work camp to Chattanooga, Tenn., under the most trying conditions . . .

It wasn't too long before Linn Yann won national (read network TV) recognition for her surprising spelling skills in her newly learned English. She earned a spot in the National Spelling Bee championships here and a call from President Reagan . . .

Linn Yann is now 15, in the eighth grade and a member of the cross-country track team at her school . . . She has even developed a Tennessee twang . . .

In the movie, Wayne Rogers and Mary Kay Place play the couple who sponsored Yann's family and Jade Chinn, a Canadian, will play Linn . . .

ABC and CBS are locked in another battle for the daytime leadership this year . . . and so far ABC is a tad ahead . . .

Through the week ending Feb. 9, ABC had a 6.2 Nielsen rating and a 21 percent audience share, compared with 6.1/21 for CBS and a 4.8/17 for NBC for the season . . .

Last week, CBS won, with ABC two-tenths of a point behind . . . The top five shows, in order: ABC's "General Hospital"; the second half of CBS' "The Price Is Right"; CBS' "The Young and the Restless" and ABC's "All My Children," tied for third; and ABC's "One Life to Live" . . .

In the bottom five, among 25 daytime programs ranked, were, in order, ABC's "Ryan's Hope," followed by its "New Love American Style"; NBC's "Search for Tomorrow"; CBS' "Press Your Luck"; and ABC's "Hot Streak" . . .

Also in the News

NBC News' "American Almanac" magazine project, back in the shop for still another overhaul, is looking for a new senior producer . . .

Sid Feders, who currently holds the job, wants to return to New York . . .

Executive producer Ed Fouhy said yesterday that he's talked to a number of people within the NBC News division and has also held "preliminary discussions" with Bob Chandler, who was senior vice president of administration at CBS News last fall when he chose to take early retirement . . .

Chandler, who held a number of important posts at CBS, had a major role in the creation of "60 Minutes," the magazine show whose success NBC has failed in 13 different attempts to emulate . . .

Among other CBS grads now working on "American Almanac" are Fouhy, anchors Connie Chung and Roger Mudd, and Gordon Manning, the NBC News executive in overall charge of the project . . .

Fouhy, however, also hinted yesterday he had talked to other prospective candidates outside NBC . . .

Fouhy takes some of the blame for the recent withdrawal of the show from the primetime schedule (it had been set for a March 4 start) when NBC News President Larry Grossman decided there weren't enough hard-hitting segments waiting on the shelf to launch a weekly version . . .

Originally, the program was formatted for a "softer" feature approach in the main, but Fouhy said yesterday there should be investigative reporting, too. "I think I misjudged it a little, you do need that mix, a little pepper" . . .

Catching Up: Betty Hudson, vice president, corporate relations and advertising at NBC, has received an honorary Doctor of Commercial Science degree from St. John's University in New York . . .

Lawrence B. Laurent, who wrote one of the first influential TV columns in the country during a 31-year career at The Washington Post, has been named director of communications for the Association of Independent Television Stations, which includes 174 independent stations around the country in its membership . . .

Laurent retired from The Post in 1982 . . .

And Gene P. Mater has been named special assistant to the director of the Commission on the Bicentennial of the United States Constitution, a title nearly as long as the document itself . . .

Mater was a CBS vice president when he took early retirement in December after more than 15 years as a senior officer of the CBS/Broadcast Group . . .