Senior managers representing the space station's international partners met Sunday to approve a plan for Europe's Jules Verne transfer vehicle to approach within 36 feet of the complex during a critical docking dress rehearsal Monday.

An illustration of Monday's demonstration. Credit: NASA/ESA

The four-hour test, called "demo day two" by the European Space Agency, will be the final step to prove the space transporter's high-tech suite of rendezvous instruments is ready for docking. Jules Verne is Europe's first Automated Transfer Vehicle, a spacecraft developed as part of a $1.9 billion program to supply the station through at least 2015.

Jules Verne pulled within 2.2 miles of the space station Saturday using its relative GPS system, which relies on precise position fixes from antennas linked with the U.S. military's fleet of navigation satellites.

The system works by feeding position data from Jules Verne and the station into the craft's flight computers, which automatically plot a course toward the complex without input from the ground.

Jules Verne performed well Saturday, giving officials confidence that the long-range rendezvous system works as expected. The only issue encountered during the demo was a propulsion glitch, a problem similar to other hiccups the ship experienced earlier in the mission. Managers said the issue was minor and don't expect it to occur again.

The international space station mission management team convened Sunday to review Saturday's demonstration and approved plans to conduct demo day two as scheduled.

"Having tested very successfully on Saturday the first part of the rendezvous, in particular using the relative GPS between that on Jules Verne and on the Russian service module of the ISS, we now have the go-ahead to test the second part of the rendezvous, which uses the optical sensors," said John Ellwood, the ATV project manager.

Monday's high-wire docking dress rehearsal will test the space tug's close-range rendezvous system, a network of futuristic laser guns and advanced computers designed to autonomously fly the spacecraft into a narrow corridor just one-half inch wide at the station's rear docking port.

"The optical sensors are the only elements of the spacecraft we have not tested yet in orbit," said Bob Chesson, head of ESA's human spaceflight and exploration operations.

But Jules Verne must first chase down the station from an "interface point" located 24.2 miles behind and three miles below the complex. Using the GPS navigation system, the ATV will leave the interface point at 1226 GMT (8:26 a.m. EDT) Monday. Jules Verne will pass through the S1 hold point by 1312 GMT (9:12 a.m. EDT), where it will begin raising its altitude to match station's orbit.

See our preliminary rendezvous timeline here.

Jules Verne will park at the S2 hold point at 1358 GMT (9:58 a.m. EDT) to begin up to a half-hour of station-keeping 2.2 miles behind the outpost. The ship will turn on its external tracking lights and activate the Russian Kurs rendezvous radar, which will provide supplemental data during the final approach.

The ship will arrive at a point about 817 feet behind the station at 1510 GMT (11:10 a.m. EDT), where it will park for about 37 minutes. During the hold, engineers at the ATV control center in Toulouse, France, will begin testing Jules Verne's four optical rendezvous instruments. Controllers will also be polled to ensure the craft is ready for the final push toward the station.

Jules Verne is scheduled to depart the S3 hold point at 1547 GMT (11:47 a.m. EDT), and the ship will begin slowing its closing rate from about one mile per hour to less than one-sixth of a mile per hour.

At that time, the ATV's navigation system will begin using data from a set of eye-like optical sensors attached to the forward end of the ship. Two videometers, working simultaneously with one in standby mode, will fire pulses of laser light toward the station one-to-ten times per second.

Acting as space mirrors, 26 reflectors positioned on the back end of the station's Zvezda service module will beam the laser light back to the sensors on Jules Verne, creating unique light patterns captured on the ATV's cameras. The patterns will allow the ATV to autonomously determine its orientation, closing rate and distance from the space station.

Two other sensors known as telegoniometers will serve as watchdogs during the final rendezvous.

The telegoniometers, similar to police radar guns, will also emit laser light at a different wavelength up to 10,000 times per second toward the reflectors. The light's travel time between Jules Verne and the station will determine range, while the direction of the station will be given by the angles of two built-in mirrors rotating to aim the laser at its target.

"We're the first vehicle which will completely automatically, using optical sensors, dock with the space station," Ellwood said before Jules Verne's March 9 launch.

The ATV's optical navigation system underwent a slate of tests on the ground to give engineers confidence the complicated sensors would work in space.

ESA tested the system using a mobile platform inside a nearly 2,000-foot-long building in France. The reflectors were attached to the platform and the ATV's optical sensors were placed on a robotic arm to imitate the spacecraft's movement.

"We did this very interesting and unique test of actually doing a real docking on the ground," Ellwood said.

ESA designed extra redundancy in the ATV's navigation system to mitigate the chances for a guidance failure close to the station, officials said.

"This is a unique technology that we've developed in Europe," Ellwood said. "We're really looking forward to seeing how it works."

Jules Verne's rendezvous technology is similar to the system employed by NASA's 2005 DART mission, which ended in failure due to a cascading list of consequences stemming from a late change in the satellite's software. The craft's flight computer improperly processed navigation data from DART's GPS and optical sensors, causing the spacecraft to lose its orientation and go off course.

DART eventually struck its rendezvous target, a retired U.S. military experimental communications satellite, before entering a retirement mode due to dwindling fuel reserves.

"DART was a totally automated vehicle. We turned it on and sent it on its way, and sure enough it had an interesting life. That is not the case with the ATV," said Mike Suffredini, NASA's space station program manager.

"It is automated, so it knows what it's supposed to do, but along the way, particularly on this flight, it's going to take certain steps and stop. We're going to look at the data, ensure it is acting the way we expect it to act and we can implement an abort and have it fly away from the space station while we figure out whatever issue that we were worried about at the time," Suffredini said.

Part of Monday's testing will focus on the ability of both the station crew and the ground controllers to intervene if something goes wrong.

Jules Verne will receive hold, retreat and resume commands a few minutes after the optical sensors become active. Such commands can be sent by the ground or the outpost's crew through a proximity communications antenna to link the ship and the station during the rendezvous.

"These are maneuvers that we could require if things don't go correctly during the rendezvous," Chesson said.

After arriving 62 feet from the station at 1613 GMT (12:13 p.m. EDT), the ATV will precisely point its Russian docking probe to line up with the station's rear docking port on Zvezda. Jules Verne should resume flying at 1628 GMT (12:28 p.m. EDT).

Jules Verne's closest approach to the complex Monday will be at a distance of 36 feet. The craft will hold there for about three minutes before Russian cosmonaut Yuri Malenchenko pushes the retreat button on a specially-designed ATV control panel inside Zvezda. The command is expected at about 1634 GMT (12:34 p.m. EDT).

After Jules Verne backs away to a point 62 feet from the station, Malenchenko will order the bus-sized spacecraft to escape the outpost's vicinity at 1638 GMT (12:38 p.m. EDT). The ship will follow a programmed series of engine firings to set up for a docking attempt Thursday.

With the assistance of station commander Peggy Whitson, Malenchenko will oversee Monday's tests through a camera system pointed at Jules Verne. The monitoring system provides the crew with an independent source of information on the rendezvous.

"It's got a different rendezvous system, so we obviously want to keep close tabs on it as it approaches," Whitson said last week.

By the end of Monday's demo, officials expect the ATV to have proven all key features of its design, including GPS and optical navigation, holds and retreats, ground- and crew-commanded escapes, and fine attitude control, Chesson said.

Engineers will also evaluate the flight monitoring software supervising the ATV's approach to the station. The system has the ability to automatically abort operations if a major problem occurs.

The station mission management team will meet again Wednesday to give a formal "go" for docking if officials are satisfied with the vehicle's performance.

Additional coverage for subscribers:
VIDEO: ARIANE 5 ROCKET BLASTS OFF WITH JULES VERNE PLAY
VIDEO: ROLLOUT OF ARIANE 5 ROCKET TO LAUNCH PAD PLAY
VIDEO: DETAILED ATV OVERVIEW BRIEFING PLAY
VIDEO: NARRATED ATV LAUNCH-TO-DOCKING ANIMATION PLAY
VIDEO: NARRATED ANIMATION OF THE RENDEZVOUS AND DOCKING PLAY
VIDEO: NARRATED ANIMATION OF ATV PERFORMING REBOOST PLAY
VIDEO: NARRATED ANIMATION OF ATV REENTRY PLAY
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