The physical and mental preparation required for space travel is immense, but for one crew member on an upcoming space shuttle mission, there is a spiritual dimension as well.

Col. Ilan Ramon, an officer in the Israeli air force and the first Israeli astronaut scheduled to fly aboard a space shuttle, also has another first to his name: He is the first astronaut to request kosher food aboard the shuttle, and he has announced his intention to observe the Sabbath while on board.

Ramon, 48, a payload specialist, is scheduled to depart Friday on a 16-day mission aboard the space shuttle Columbia, although the launch might be delayed because of mechanical problems. He plans to conduct more than 140 experiments in the space, life and physical sciences.

A series of complications immediately arose when Ramon considered how he would observe Shabbat, the Jewish Sabbath, which lasts from sundown Friday to sundown Saturday each week. Jews observe the day with blessings over bread and wine, candle lighting, prayer services and a cessation of work.

The major problem for Ramon is that the shuttle will orbit the Earth every 90 minutes, so technically a "day" will pass each hour and a half. Shabbat is observed every seventh "day," so Ramon could find himself quite busy.

Ramon has said that he is not especially religious but that nonetheless it is important as "an act of solidarity with the Jewish tradition" to observe Shabbat in some way during his mission.

Ramon sought the help of a rabbi on the so-called Space Coast in Cape Canaveral, Fla., where he trained before moving to the Johnson Space Center in Houston for final training.

Rabbi Zvi Konikov, a member of the Hasidic Lubavitcher movement, worked with Ramon and prepared a letter to send to a respected group of rabbis, called poskim, who could rule on the situation according to Halacha, or Jewish law.

Rabbis had discussed and debated the issue before, but though there have been other Jewish astronauts, none had ever expressed the desire to observe Shabbat while on a mission.

"It was always reserved for a theoretical," Konikov said. "This is the first time that it's actually happening.

"For someone to be interested in how he can keep the Sabbath even though he is not necessarily a very religious person, I find that tremendous," added Konikov, who with the help of a rabbi in New York has collected responses from a half-dozen poskim, several of whom conveyed their interpretations by phone.

A consensus has emerged from the responses, though the final ruling will not be made until more rabbis have responded.

The prevailing opinion is that the time is not based on when a person sees the sun set, but on the 24-hour rotation of the Earth, Konikov said.

Therefore, the rabbis generally agree that regardless of Ramon's speed of travel around the Earth, the Earth is continuing to rotate at the same pace. So his Shabbat responsibilities would come every seven days, as clocked in the Eastern time zone, where Cape Canaveral, the launch site, is located.

Rabbi Levy Yitzhak Halperin, who is the head of the Israel-based Institute of Science and Halacha, disagreed somewhat, arguing that because Ramon is Israeli, he could keep time in sync with his homeland.

Ramon was not available for interviews because he is in final preparations for the mission. However, he released a statement outlining the reasoning behind his request for kosher food and Shabbat observance.

"As an Israeli and a Jew I asked NASA if it would be possible to supply kosher food for my menu in space," the statement read. "I was surprised and overwhelmed with the effort NASA put in trying to accommodate my request. NASA has found kosher food suitable to fly in space and will supply me with kosher food during the flight."

Ramon was careful to say that he would "probably" observe Shabbat in some fashion, because of his significant flight responsibilities. He also said that because astronauts keep time according to their training schedule in Houston, he will observe Shabbat according to that clock, which is one hour behind Cape Canaveral time.

"As far as practicing the Sabbath -- as an act of solidarity with the Jewish tradition -- I will probably try to make a symbolic kiddush [blessing over wine] in space, if time and flight plan schedule permit," he said.

Konikov, who at Ramon's request will bless the astronaut on the day of the launch, said the final ruling by the rabbis might persuade Ramon to count time from Cape Canaveral instead of Houston.

"When he hears from me the final Halacha, he'll abide by that, which is only an hour off and wouldn't be any interference," he said.

Regardless of how Ramon practices, Konikov said, the fact that he pursued the question and wants to have solidarity with his people signifies a special moment for Jews worldwide.

"I think it's going to mean a lot, especially to the so-called modern generation, thinking that science, medicine and modern technology was a contradiction to traditional observance," he said.

"It's a small step by Colonel Ramon but a large step for Judaism and mankind," he said.

Ilan Ramon is to depart Friday on the space shuttle Columbia. There have been other Jewish astronauts, but none expressed the desire to observe the Sabbath or keep kosher.