Countdown resumed – update 2 December 18:00 CET

On Thursday, a Vega rocket will boost LISA Pathfinder into space to pave the way to a future mission for detecting gravitational waves. Once aloft, ESA’s mission control teams will pace the ultra high-tech spacecraft through the critical first days of the journey to its final destination.

At 04:04 GMT (05:04 CET) on Thursday, 3 December, ESA’s LISA Pathfinder is set to lift off on a 30 m-tall Vega rocket from Europe’s Spaceport in Kourou, French Guiana, for a 105-minute ride into orbit.

Liftoff was previously planned for 2 December, but was delayed by one day to thoroughly check a technical issue with the launcher.

LISA Pathfinder ready for launch. Final preparations are under way at Europe's Spaceport in Kourou, French Guiana, for the launch of LISA Pathfinder, ESA's technology demonstrator that will pave the way for detecting gravitational waves from space. Liftoff is planned at 04:15 GMT (05:15 CET) on 2 December. In this image, taken with an ultra-wide angle fisheye lens on 19 November, the spacecraft is hidden from view, encapsulated in the ‘upper composite’ of its Vega rocket. Only the aerodynamic fairing at the top of the fully assembled launcher is visible, while the lower stages are hidden by the movable access platform. The hose is part of the air conditioning system that regulates the environment inside the fairing. Credit: ESA–M. Pedoussaut, 2015

LISA Pathfinder ready for launch. In this image, taken with an ultra-wide angle fisheye lens on 19 November, the spacecraft is hidden from view, encapsulated in the ‘upper composite’ of its Vega rocket. Credit: ESA–M. Pedoussaut, 2015

LISA Pathfinder is a demonstrator to help open up a completely new window into the Universe: it will test new technologies needed to measure gravitational waves in space. Predicted by Albert Einstein, these waves are ripples in the curvature of spacetime produced by massive celestial events, such as the merging of black holes.

Detecting gravitational waves would be an additional confirmation of General Relativity, and greatly improve our knowledge of the most powerful phenomena in the Universe.

Separation from Vega is expected at 05:49 GMT (06:49 CET), marking the moment when controllers at ESA’s ESOC operations centre in Darmstadt, Germany, take over the satellite.

First contact is expected two minutes later, around 05:51 GMT (06:51 CET) via the ESA’s Estrack station in Kourou, French Guyana.

After confirming LISA Pathfinder’s status and overall health, ground teams will start an intensive cycle of crucial and complex orbit-raising manoeuvres.

These will include firing the mission’s propulsion module six times during mid-December to raise its initial orbit, before beginning a six-week cruise phase to its operational orbit some 1.5 million km from Earth in a sunward direction.

After arriving at the final working orbit, the propulsion module will be discarded in later January, and, after about three months of setting-up and calibration, the science mission will begin in March.

Watch live

The liftoff will be streamed live via two separate programmes on Wednesday: launch webcast live from Kourou, 03:44 GMT (04:44 CET) start; and a media briefing live from ESOC, 05:30 GMT (06:30 CET) start (links to both via

The timeline below is subject to change.

1-2 December 2015

LISA Pathfinder/ESOC Tracking stations
L-09:10:00 18:54:00 19:54:00 Flight Control Team ‘on console’ in ESOC Main Control Room; start of prelaunch activities (B-section) xx
L-09:00:00 19:04:00 20:04:00 ESOC teams begin monitoring spacecraft and ground systems, receiving live telemetry from LISA Pathfinder on top of Vega via umbilical
L-08:00:00 20:04:00 21:04:00 Start of Vega countdown
L-06:00:00 22:04:00 23:04:00 Start of ESOC network countdown; mission controllers continue monitoring LISA Pathfinder Ground tracking stations: Start of dedicated LPF launch support. Begin station check outs at ESA 15m stations at Perth (Aus), Maspalomas (Spain), Kourou (F. Guiana) plus ASI station Malindi (Kenya)
L-05:45:00 22:19:00 23:19:00 ESOC starts a series of data flow tests to confirm primary & backup data links between ESOC and tracking stations Data flow tests KRU, MAS, PER, MAL-X
L-05:30:00 22:34:00 23:34:00 Activation of Vega Multi Function Unit – MFU controls the launcher’s critical systems (incl power distribution & pyrotechnics)
L-05:10:00 22:54:00 23:54:00 “Vega Inertial Reference System on;
Vega telemetry starts flowing”
L-05:05:00 22:59:00 23:59:00 ESOC Flight Director conducts first formal check of ground segment launch readiness: confirms that teams, systems and stations are ready Data flow tests continue: test back-up links to stations
L-04:55:00 23:09:00 00:09:00 ESOC Flight Director reports ground segment status to Kourou launch control centre
L-04:50:00 23:14:00 00:14:00 Activation of Vega Safeguard Master Unit – SMU controls safety self-destruct, which can be commanded by ground or autonomously in case of degraded flight behaviour
L-04:20:00 23:44:00 00:44:00 Activation of Vega onboard computer and loading of flight program
L-03:45:00 00:19:00 01:19:00 End of data flow tests via back-up station links. Links now configured for actual LPF TM. Begin data flow tests on primary links.
L-02:40:00 01:24:00 02:24:00 Mobile gantry withdrawal (45 mins)
L-02:30:00 01:34:00 02:34:00 End of data flow tests via primary station links. Links now configured for actual LPF TM. All data flow tests complete; ground segment configured for actual LPF TM
L-02:00:00 02:04:00 03:04:00 Mission Control Team handover in ESOC MCR. A-Section engineers briefed by B-Section counterparts.
L-01:45:00 02:19:00 03:19:00 A-Section of Mission Control Team now on console in MCR Station engineer team at Kourou depart for safe area. From now until launch, KRU station operated remotely from ESOC.
L-01:55:00 02:09:00 03:09:00 Alignment and checks of Inertial Reference System (after withdrawal of gantry)
L-01:15:00 02:49:00 03:49:00 “Vega telemetry transmitter on (after withdrawal of gantry)
Vega transponders on”
L-00:55:00 03:09:00 04:09:00 ESA Flight Director conducts Go/NoGo roll call in Main Control Room
L-00:35:00 03:29:00 04:29:00 ESOC Spacecraft Operations Manager conducts final briefing with ground tracking stations All stations in conference with ESOC
L-00:34:00 03:30:00 04:30:00 Launcher system ready
L-00:25:00 03:39:00 04:39:00 ESOC Flight Director conducts final formal check of ground segment launch readiness: confirms that teams, systems and stations are ready
L-00:15:00 03:49:00 04:49:00 LISA Pathfinder on internal power ESOC Flight Director confirms ground segment ready for launch to Kourou launch control centre
L-00:10:00 03:54:00 04:54:00 Last Kourou weather report before launch
L-00:04:00 04:00:00 05:00:00 Start of Vega synchronized sequence
L-00:00:08 04:03:52 05:03:52 Last possible launch abort
00:00:00 04:04:00 05:04:00 Vega first stage ignition
L+00:00:01 04:04:01 05:04:01 LIFT OFF
L+00:01:53 04:05:53 05:05:53 Separation of first stage
L+00:01:54 04:05:54 05:05:54 Second stage ignition
L+00:02:30 04:06:30 05:06:30 All tracking stations configured for AOS – first acquisition of signal
L+00:03:37 04:07:37 05:07:37 Separation of second stage
L+00:03:49 04:07:49 05:07:49 Third stage ignition
L+00:04:03 04:08:03 05:08:03 Fairing jettisoned
L+00:06:30 04:10:30 05:10:30 Separation of third stage
L+00:07:29 04:11:29 05:11:29 Fourth stage first burn
L+00:16:23 04:20:23 05:20:23 Fourth stage shutdown
L+01:41:19 05:45:19 06:45:19 Fourth stage second burn
L+01:42:53 05:46:53 06:46:53 Fourth stage second shutdown
L+01:45:33 05:49:33 06:49:33 LISA Pathfinder release command
L+01:45:33 05:49:33 06:49:33 SEPARATION LISA Pathfinder separates from fourth stage; begins automatic sequence
L+01:47:03 05:51:03 06:51:03 AOS Acquisition of signal (earliest) from satellite via Kourou station KRU AOS LPF
L+01:48:00 05:52:00 06:52:00 ESOC issues test command “KRU transmits test command
KRU starts ranging & Doppler for orbit determination”
L+01:55:10 05:59:10 06:59:10 Fourth stage third burn, for deorbiting
L+01:55:17 05:59:17 06:59:17 Fourth stage shutdown
L+02:10:00 06:14:00 07:14:00 LISA Pathfinder end of automatic sequence. In stable, Sun-pointing mode. ESOC teams continue checkout
CET offset = 01:00:00
Vega launcher is also tracked by separate dedicated stations. These are not indicated in this timeline.
LCC: Launcher Control Centre, Jupiter Control Room, Kourou, French Guyana
ESOC: European Space Operations Centre, Darmstadt, Germany
OD: ESA Flight Operations Director in Main Control Room
VV06: Arianespace Vega launcher flight VV06
MET: Mission Elapsed Time – before/after liftoff times are -/+
LPF: LISA Pathfinder spacecraft
AOS: Acquisition of signal
LOS: Loss of signal
MCR: Main Control Room at ESOC
OM: ESA Ground Operations Manager in Main Control Room
SOM: ESA Spacecraft Operations Manager in Main Control Room
KRU: ESA Estrack station, Kourou