THIS business of hosting the Centennial Olympic Games now gets serious in Atlanta. The one-year countdown begins tomorrow (July 19). Soon after, a month-long shakedown ''cruise'' called Atlanta Sports '95 will test the readiness of many facilities and volunteers.
Atlanta Sports '95 is a series of major international sports competitions, everything from the US Open Badminton Championships at Georgia State University to the Pan Pacific Swimming meet at Georgia Tech. Some of these events will overlap, but it won't be anything like next summer, when everything might seem to be happening at once, which is the beauty and supreme challenge of the Olympics.
And speaking of challenges, the Atlanta Committee for the Olympic Games (ACOG) faces its share. Two of the six dormitories built for Olympic athletes have settled more than normal, a situation one official calls ''unusual,'' though ''not insurmountable.'' The Olympic drug-testing lab that was supposed to be up and running this summer has not yet been accredited by the International Olympic Committee, and an effort to sell bricks for a 60-acre downtown Olympic Centennial Park is lagging way behind.
There are bright signs, too. Sales of licensed Olympic merchandise already have surpassed $250 million, which exceeds the total sales figure for the 1984 Los Angeles Games. Ticket orders also have been very encouraging. Demand has been high, unexpectedly so, for such low-profile sports as field hockey, judo, and badminton.
''Those who doubted the American appetite for European- and Asian-dominated sports, or our interest in seeing them, need to rethink their concept,'' says Scott Anderson, ACOG's ticket chief. ''When it comes to the Olympic Games, people just want to go.''
The new Mickey Mantle
MICKEY MANTLE, whose physical trials have been well documented of late, said last week in Dallas that he's going to make amends for being a poor role model to young people. Mantle recently underwent major surgery, but even before that he appeared to be putting his life in order after years of carousing.
''I'm going to spend the rest of my life trying to make up,'' he said at a press conference held in conjunction with the All-Star Game. ''I want to start giving something back. What I want to do now is give the word to the kids not to drink, do drugs, or anything like that. I think the family - mom and dad - ought to be the role model.''
It's heartening to see the about-face Mantle is making, especially given his personal prominence. Mantle has remained a popular sports icon through the years, an immensely talented athlete whose name and association with the Yankees practically assured his legend.
Though known as a slugger, he was also a superb fielder whose glove work played a key role in one of the most memorable games in baseball history. ''How can anyone ever forget the catch he made on Gil Hodges's line drive to save Don Larsen's perfect game?'' former Yankee shortstop Tony Kubek asks.
In his enjoyable reminiscence, ''Sixty-One: The Team, the Record, the Men'' (Fireside Books, 1989, written with Terry Pluto) Kubek says that Mantle could throw such an elusive knuckle ball that Yogi Berra wouldn't catch him.
Another teammate, Whitey Ford, remembers an inane question once directed at Mantle after a bad game during which he struck out, popped up, and kicked the water cooler. ''Hey, Mick,'' a reporter asked, ''was that pop-up in the third inning the highest one you ever hit?''
Touching other bases
* Pop quiz: Name the official TV game shows of the 1996 Atlanta Olympics. (Answer below.)
* Backpacker magazine says that a plastic garbage bag is indispensable on the trail. Bags can be multipurpose lifesavers for hikers in trouble, serving as a bivouac sack, rain jacket, and an insulator when stuffed with leaves or grass. Backpacker says hikers should always carry two other items, too: a lighter and a knife.
* Here's an interesting sports address: Canadian Figure Skating Association, 1600 James Naismith Drive, Gloucester, Ontario, Canada. Naismith invented basketball in Springfield, Mass., more than a century ago. What many Americans probably don't realize is that Naismith was born near Ottawa.
* Two weekend developments that deserve attention: 1) Annika Sorenstam, a member of a strong Swedish contingent on the American women's golf tour, overtook Meg Mallon for a one-shot victory in the US Women's Open played in Colorado Springs, Colo.; and 2) the US men's soccer team scored a stunning victory in the Copa America in Uruguay, beating Argentina, 3-0, in a score heard 'round the soccer-playing world.
* Quiz answer: ''Wheel of Fortune'' and ''Jeopardy!'' Go figure.