Schumacher, Formula One's most successful driver, had to abandon a planned comeback as a stand-in with Ferrari last season due to the lingering effects of a neck injury suffered in a motorcycle accident.
He has since signed a multi-year deal with Mercedes, who have taken over Brawn, as world champion Jenson Button's replacement.
"Despite the weather not being what we all would have liked all my senses were nevertheless on full alert - this alone was worth it," he said.
"I felt comfortable out on the track from the very beginning.
"We have two purposes, one is to get as many kilometres as possible for myself and the second priority is to get to know the engineers and get to work together."
Further testing sessions were scheduled for Wednesday and Thursday.
Schumacher said he was settling in well and preparations for the new season were on track during the GP2 development car test.
GP2 is Formula's One's support series at race weekends, with all teams using the same Renault-powered cars.
Formula One teams are not allowed to test until the first official session in Valencia on February 1.