ESA News
http://www.esa.int

20 March 2008

Shooting a Par-3 hole in space: Three steps to ATV docking

Jules Verne ATV is lining up for Europe's first-ever automated docking in
space. Following two demonstrations, the final 'putt' must be more accurate
and gentle than on any rolling golf green.

Now that the vessel is 'on the green' -- in a parking orbit 2000 m ahead of
the ISS -- ATV mission controllers must pace the spacecraft through two
pending and crucial demonstration dockings, moving successively closer to
the ISS, and then finally go for an actual rendezvous and docking attempt on
3 April.

ATV Control Centre: tight teamwork
 
Imagine the muscles, tendons, nerves and bones that must work in exquisite
coordination and timing in a golfer's body to cause the ball to ultimately
roll into the hole. It's the same with the ATV rendezvous and docking: A
large number of people, computers, networks and systems must work in tight
synchronisation -- with fraction-of-a-second timing -- to set Jules Verne on
the last automatic leg of its docking.

The challenge is enormous and a successful first attempt will depend on very
tight teamwork, excellent coordination and a superb understanding of the
spacecraft and its complex automated control systems.

"The spacecraft is functioning perfectly, the team is very well trained and
we are looking forward to an excellent first docking attempt on 3 April. It
will be complex, but after our successful launch and early orbit phase, and
the transfer to the parking orbit, the entire team here on the ground has
gained a lot of confidence in themselves and in Jules Verne," says Alberto
Novelli, ESA's Mission Director at the ATV Control Centre (ATV-CC) in
Toulouse, France.

The ATV's automated Collision Avoidance Manoeuvre (CAM) capability was
successfully tested in-flight on 14 March, and other functions of the
sophisticated docking control system will be tested in two Demonstration
Days, on 29 and 31 March. The manoeuvres are planned using a series of
way-points and station points in the vicinity of the ISS, indicated as S-1,
S0, S1, S2 and so on, which map out a complex series of dynamic orbital
trajectories and zones.

Note all times and dates subject to change.

Demonstration Day 1: 29 March - 16:34 CET [1534 UTC]

The main purpose of Demo Day 1 is to test the ATV's Guidance & Navigation
System; the test will be commanded from ATV-CC. This is expected to show
that the ATV can perform relative navigation with the ISS using relative GPS
(global positioning satellites) to successfully and safely manoeuvre ATV to
station point S2, located 3500 m behind the ISS and at the same orbital
altitude.

After Demo Day 1, the results will be assessed by the ESA JADOR (Jules Verne
ATV Demonstration Objectives Report) team and submitted to the ISS Mission
Management Team; after an assessment and authorisation on 30 March, ATV can
proceed to Demo Day 2.

Demonstration Day 2: 31 March - 14:40 CEST [1240 UTC]
 
The main purpose of Demo Day 2 is to test the Close Range Sensors and ATV's
Guidance & Navigation System; the test will also include practising
contingency procedures commanded by ATV-CC and by the ISS crew, as well as
ATV close proximity manoeuvring. ATV will be commanded to close to S4, 12 m
from the docking port of Zvezda (the ISS Russian Service Module), then go
back to S4, and finally an 'Escape' manoeuvre will be commanded to take ATV
away from and around the ISS and back to station point S1.

Once ATV has been assessed as fully ready for docking, the first attempt is
scheduled to be made for 3 April.

The docking procedure will begin at 13:44 CEST [1144 UTC], with ATV starting
from station point S3, 250 m from the ISS. The ATV computers will use use
Videometer and Telegoniometer data for an automated final approach and
docking. ATV will slow down to 7 cm/second as it closes to within a few
metres of the Russian module. ATV-CC mission controllers will direct the ATV
in a step-by-step predefined approach, and will seek authorisation from the
Russian Mission Control Centre in Moscow (MCC-M) before final contact.

At all stages, the ISS crew will be deeply involved. Their tasks will
include control and monitoring of the ATV during Demo Day 1, 2 and docking,
preparation of the Russian module for docking and issuing specific ATV
commands, such as Abort, Hold, Retreat or Escape, when requested.

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