Editor's note: Click here to see who does what in the rescue teams
Copiapo, Chile (CNN) -- As night breaks into day, the arc lights on three drilling rigs flicker off.
Seven hundred meters (2,300 feet) beneath the surface, 33 miners begin another day trapped in the bowels of the San Jose gold and copper mine.
The mine caved in on August 5 and Chilean rescue teams spent the next 17 days probing down from the desert above to find out if the men were dead or alive. They were cut off from the outside world but the miners never lost notion of time.
"The miners had cellphones, so they had a calendar. The medics say they knew perfectly well what day it was and what time it was. The only thing they didn't know was what the weather was like on the surface," said Miguel Fortt, a mining consultant and the man who coordinated the first phase of the search effort.
The 33 men have split into three shifts. The day shift works from 8 a.m. to 4 p.m. The evening shift runs from 4 p.m. to midnight. And the night shift lasts from midnight to 8 a.m.
Each shift is headed by a foreman. The largest group has 12, another has 11 and the third unit has 10 men.
"They have eight hours to rest when they must put out the lights. They have another eight hour work shift and then eight hours to play games, read or write letters, jog or have a walk," Fortt told CNN, sitting on a rock at the entrance to the San Jose mine in Chile's northern Atacama desert.
Before 8 a.m., ahead of the start of day shift, some of the men make their way from the Camp on Level 80 up to "Refuge 33" on Level 100 -- a distance of some 180 meters.
Immediately after the mine collapse the men huddled and slept for days in the 50 square meter (500 meter) refuge. Now, an area of that shelter is set aside for showers but the miners have moved their living and sleeping quarters deeper down.
Washing water is piped down 700 meters (2,300 feet) from the surface to the refuge once it has been heated by a solar-powered heater. As excess water runs deeper into the mine it evaporates and forces dust to settle and above all lowers the temperature.
The temperature in the camp, where the trapped miners eat and sleep, is currently running at a cool 15 to 18 degrees Celsius. Higher up the mine just above the refuge and in the workshop, temperatures hit around 30 Celsius, according to Fortt.
"In the upper levels, the air temperature is equivalent to being in Ecuador or Cancun. That's the tropics. Lower down it's cooler -- like being in Chile or New Zealand," he said.
Around 7.45 a.m., quarter of an hour before day shift starts, breakfast drops into the refuge via one of two eight centimeter boreholes.
Rescuers call the boreholes "umbilical chords." Round the clock they drop 2.5-meter long metal cylinders, dubbed "carrier pigeons," down the boreholes taking food, water, clothes and letters to the miners.
Each shift has three or four men assigned to receiving the "carrier pigeons." They have about five minutes to unload the cylinders and then store the contents.
Breakfast is always a protein shake and sometimes there's a jam sandwich too.
When the work day begins, the miners have no time to dwell on the ordeal that has befallen them. There's work to be done. The miners are helping to rescue themselves.
The first job is for the environmental assistant and the gas checker to walk through the tunnels monitoring ventilation and air quality. Medics are pumping down air from the surface with a 18 to 22 percent oxygen mix.
Any change to air quality in the mine means rescuers have to adjust their mix from above ground.
Around the same time, miner Yonni Barrios, an explosives expert with paramedic training, begins his rounds. His comrades jokingly call him "Dr. House," after the U.S. TV series.
He must check all the miners' vital signs and do daily tests as well as keeping a close watch on the men's weight.
"Yonni has to do blood and urine tests and check if there's any skin infection; these are analyzed by a paramedic and then sent up to the surface," Fortt said.
The heaviest work in recent days has been up on level 135 in the workshop, about a 220-meter walk from the refuge. Last Friday, a 12-inch drill bit punched through the roof of the workshop -- part of the so-called Plan B effort to drill and escape shaft and hoist the men out.
The drilling has sent rocks, debris and water crashing into the workshop, so now teams using two mechanical "scoops" and a front loader must clear that away.
Around mid-morning, a snack break. Rescuers usually send down a fruit and cereal milkshake. On the surface, nurse Mabel Rios is supervising the dispatches.
"About 7.45 a.m. we send them breakfast. At 10 a.m. a milkshake and at 12 midday we send them lunch. Around 4 p.m we give them another milkshake and around p.m. we sending them their dinner," Rios told CNN, seated a few yards from the entrance to one of the boreholes on an earthen platform that overlooked Plan B and Plan C drill sites.
Day shift ends at 4 p.m., time for the miners to relax. They have games of dice, cards and dominoes. They can listen to MP3 players loaded with folk tunes and Latino pop songs or watch old football games and movies on a handheld projector capable of beaming a 21-inch image onto the cavern wall.
But they must exercise too. Up on the surface a personal trainer has been assigned to the men, who orders them to jog or do other exercises.
Electrician Edison Pena, a die-hard Elvis Presley fan, seems to have emerged as one of the mine's top sportsmen, according to Fortt. He jogs an hour a day up and down some 2-1/2 kilometers of tunnels that are still safely accessible.
"Usually the truck operators are quite fat because they sit down all day. So they have a personal trainer to help them cut down their waistline so that when the day comes they can fit into the rescue capsule," Fortt said.
Not all are as healthy as Pena. In the group there are at least 14 smokers, according to nurse Rios. At first two of those received nicotine patches but then they demanded real cigarettes.
Rios now sends down each of the smokers a personal ration of 11 low-tar cigarettes, of the locally available Viceroy or Belmont brands. There's a catch though. The smokers face a long hike upwards to the smoking area -- more than half a kilometer from the camp.
"They're well organized because there are people who don't smoke and they don't like to have people smoking close by. So the smoking sector is well separated," Rios said.
Not only is the smoking area far from the living quarters, it's also one of the hottest parts of the mine where temperatures hover around 30 Celsius.
Perhaps one of the miners' key pastimes when they're not working, is writing letters to their loved ones above.
"They're very concerned that we should send them pens and paper. They love to write and they're writing a lot. Some of them write every day," Rios said.
The miners have to send their mail to the surface in one of the carrier pigeons before midday. Their missives are wrapped in thick black plastic to stop the pages getting wet on the ride up.
Around 8 p.m. families, camped out on the surface in "Camp Hope" a tent village at the mine entrance, send fresh news and letters down into the earth.
Sometime around midnight, before they sleep, the miners are once again replying to wives, parents and children in the world above.
It's around that time too that each of the men feels a little lonely and allows his mind to wander, according to Fortt, a rescue expert who has himself been trapped in mine cave-ins.
"Each one of them has had plenty of time to think what to do with the rest of their lives. When they get out of the mine, the second chapter of their lives is about to begin," he said.
"They'll have to make some radical changes because they won't live to tell a tale like this a second time."