Shooting A Par-3 Hole
In Space: Three Steps To ATV Docking
(20 March 2008) 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.
Demo Day 1 will bring ATV to s2, 3500 m behind the ISS. Demo Day 2 will bring ATV to S41, just 12 m away from the Russian service module. The first docking attempt is scheduled for 3 April 2008. ATV will slow down to just 7 cm/sec before final contact. (courtesy: ESA)
ATV Control Centre: tight
teamwork
Imagine the muscles, tendons, nerves and bones that must
work in exquisite co-ordination 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.
Alberto Novelli, Head of ATV Mission Operations (courtesy: ESA)
The challenge is enormous and a successful
first attempt will depend on very tight teamwork, excellent co-ordination 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.
The Automated Transfer Vehicle (ATV) is the first fully automatic re-supply spacecraft of its kind. ESA's Jules Verne ATV is the first European space supplier for the ISS. Its launch is scheduled on 9 March from Europe's spaceport in Kourou, French Guiana. (courtesy: ESA - D.Ducros)
Demonstration Day 1 - 29 March - 16:34
CET
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.
Artist's impression of ATV approaching for rendezvous with ISS (courtesy: ESA TV)
Demonstration Day 2 - 31 March - 14:40
CEST
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.
Docking - 3 April - 16:20 CEST
The
docking procedure will begin at 13:44 CEST, 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.
(source: ESA)
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