TUCSON, Ariz. - NASA couldn't send commands to the Phoenix Mars lander most of yesterday because of a radio glitch, delaying a second day of activities, officials said.

The minor problem was fixed later in the day, and the Mars Reconnaissance orbiter resumed relaying the lander's images of the Martian landscape back to Earth, said NASA officials said.

Phoenix, the latest spacecraft on Mars, communicates with scientists through two NASA orbiters circling the planet.

The Reconnaissance orbiter earlier had turned its radio off, possibly because of a cosmic ray, said Fuk Li, manager of the Mars exploration program for NASA's Jet Propulsion Laboratory in Pasadena, Calif. Li said the orbiter was programmed to respond as it did.

"All this is a one-day hiccup in being able to move the arm around, so it's no big deal," said Ed Sedivy, Phoenix program manager at Lockheed Martin Space Systems Co.

Even with the glitch fixed, laboratory spokeswoman Veronica McGregor said the second orbiter, the Mars Odyssey, would be used today to send commands to Phoenix during its morning orbital pass. It will tell the lander to begin unstowing its robotic arm.

Since landing on Mars on Sunday, Phoenix has delighted scientists with the first-ever peek of the planet's northern arctic region. The terrain where Phoenix settled is relatively flat, with polygon-shaped patterns in the ground probably caused by the expansion and contraction of underground ice.

Peter Smith of the University of Arizona, the mission's principal researcher, and his colleague Alfred McEwen, who operates the camera aboard the Mars Reconnaissance Orbiter, said photos taken since the landing show that Phoenix is at the edge of a trough that will make an ideal place for digging.

Smith said plans had called for maneuvers yesterday to unhook the lander's 8-foot robotic arm from a protective sleeve that held it in place. The arm is at the heart of the lander's scientific functions during its three-month experiment.

Phoenix will dig into the soil with the arm to reach ice believed to be buried inches to a foot deep, as part of the effort to study whether the site could have supported primitive life. Among the things it will look for is whether the ice melted in Mars' history.