His 24th news conference, and the first of his second year in office, came on a day when all seemed well for Jimmy Carter.

On Capitol Hill, the advice and consent process was going his way. In one hearing room, senators of both parties were falling over themselves to praise his nominee for FBI director, Judge William Webster. The judge, whose well-scrubbed, buttoned-down looks and quietly respectful demeanor make him the traditioal model of an FBI man, almost ducked in aw-shucks embarrassment when Strom Thurmond described him as a "straight arrow." But he didn't deny it, and his answers were impressively direct. He made an excellent witness. His stated beliefs about such things as individual rights and police powers made it apparent the president had chosen exceptionally well.

In another hearing room, it was clear sailing for a second Carter appointee. Frank Carlucci, whom the president has picked to be the Central Intelligence Agency's deputy director, giving him the day-to-day management of that troubled agency, won the unanimous endorsement of the Senate Intolligence Committee. It was just a year ago that Senate opposition gave Carter his first presidential seback and forced his choice for CIA chief, Theodore C. Sorenson, to withdraw. That defeat had signaled trouble ahead for Carter in his relationships with Congress. Now, 12 months later, harmony seems to prevail.

From the Middle East, where hopes and fears rise and fall in daily cycles of joy and gloom, the news was momentarily more encouraging. And the president's role as conciliator became more significanta as time passed. He was preparing to greet Anwar Sadat in Washington and then spend the weekend discussing war and peace in the Middle east with the Egyptian leader at Camp David.

At home and abroad, the president was in command. A good setting for another newss session with the reporters.

Jimmy Carter's best performances have been at his press conferences. His style and temperament are particularly well suited to that forum - he conveys information easily and surely and rarely stumbles or shows stress.

The president has taken to using the opening minutes of his news conferences for prepared statements - short speeches, actually, usually more effective that his formal appearances. He second, especially, was vintage Carter, the engineer president displaying his strengths.

In narrative form, lucidly and calmly, tahe president told tahe story of what was known about the Soviet satellite and its re-entry into the earth's atmosphere. It was quite a story, and the president told it well.

This was a true-life drama, with high stakes and played out in secrecy for more than a month. In the retelling, of course, the president was letting us know how effectively his team had functioned: the careful monitoring, the personal discussions with the Russians, the private notification ofa key congressional leaders and selected allies around the world, the coolness under pressure, the final confident handling of potential crisis.

"Early on the morning of the 24th," he said, "I was notified that the satellite would enter the atmosphere quite early. We did not know whether it would hit between Hawaii, or on a very high curve up to the northern part of Canada, ora the western coast of Africa, because sometimes the sattellites can skip from one place to an other as they enter the atmosphere. It, as you know, entered the atmosphere in Canada."

He quietly detailed the steps then taken, and described the problems facing humanity from atomic-powered satellites: our last such satellite was put into orbit 13 years ago and then raised into a higher orbit after its useful work was completed, thus consigning it to circling the globe for at least anothe 4,000 years.

At the end the president was eloquent in his appeal for "more rigid safety precautions . . . among all nataions in earth-orbiting satellites." And, in terms that any layman easily could understand, he explained some of the intricacies of the only conceivable American need for an atomic-powered satellite - for space probes to the outer planets, when energy from the sun alone would not last long enough. His conclusion was brief, and pointed.

We should not continue with earth-orbiting satellites "unless much more advanced safety precautions can be initiated."

All in all it was an extraordinarily effective example of how a president can inform the public on a matter of current concern and long-term importance.

Then Jimmy Carter came back to earth.

Zip-zap, zip-zap came the tattoo of questions about the unseemly Marston case. His handling of the case, his methods, his standards, his pledges, even his veracity were all called into question. To this viewer, watching the president close up on television, it was a tight-lipped and stung Jimmy Carter who fended off the questioners. Fend off isn't really correct; he brushed them aside. He was quietly defiant: "I see nothing improper in the handling of the case". . . "No, I don't (see any conflict in his public statements on the case)". . . "I do think that our actions are compatible with my campaign statements". . . "If it occurred now, I would do the same."

Toward the end, after incessant parrying and thrusting, a questioner returned to the Russian satellite. Could the president resolve the convlicting reports coming out of Canada?

"I know of nothing at this point that hasn't already been put into the press," he replied. Was the satellite then being retrieved? "I do not know."

Jimmy Carter had just demonstrated two sides of his character. He is refreshingly capable of saying publicly he doesn't know the answer. And he is also capable, in this case at least, of balking at conceding any possible error.