A tiny robot helpers to assist astronauts in daily chores and to buzz around their orbiting outpost, monitoring its condition was developed by the engineers at the National Aeronautics and Space Administration's Ames Research Center at Moffett Field, Calif., The small robot buddies tag along with astronauts and act as personal assistants.

The robot about the size of softballs are propelled by tiny fans through the weightlessness of a space station or shuttle. Hovering over the astronauts' shoulders and responding to voice commands, the devices, equipped with cameras, speakers, microphones and a variety of sensors, could serve as additional sets of eyes, ears and noses for the crew in space and the support staff on the ground.

The jobs imagined for these robot aides range from the essential to the mundane. As an astronaut works on an experiment with both hands in a glove box, for instance, the mechanical assistant could serve as a communications link with an Earth-bound researcher watching from afar.

The devices could also patrol the corridors of the space station, checking for gas leaks, smoke and unusual bacterial growth, or remind astronauts about the next tasks on their daily to-do lists or of the need to send a birthday message to a loved one at home. The device, as now envisioned, is a ball about 5 inches in diameter that is studded with sensors for rangefinders, motion detectors and position trackers to keep it from running into things or getting lost. The battery-powered P.S.A. could move in any direction using six enclosed propeller fans and have a flat-screen video panel on one side to display data.

It would be impossible for each P.S.A. to carry the computing power and instruments for all the things people suggest these helpers could do, which is where the wireless data network comes into play. The robots would operate from a base station that would contain powerful computers for analyzing sensor data, running speech-recognition and voice-synthesizer software, relaying communications and tracking the devices. The station would also contain docking ports for recharging the P.S.A.'s batteries, and sensors that could be snapped onto the robots, depending on tasks assigned to them.