  For the technology development of the mission EXCEDE (EXoplanetary
Circumstellar Environments and Disk Explorer) - a 0.7 m telescope equipped with
a Phase-Induced Amplitude Apodization Coronagraph (PIAA-C) and a 2000-element
MEMS deformable mirror, capable of raw contrasts of 1e-6 at 1.2 lambda/D and
1e-7 above 2 lambda/D - we developed two test benches simulating its key
components, one in air, the other in vacuum. To achieve this level of contrast,
one of the main goals is to remove low-order aberrations, using a Low-Order
WaveFront Sensor (LOWFS). We tested this key component, together with the
coronagraph and the wavefront control, in air at NASA Ames Research Center and
in vacuum at Lockheed Martin. The LOWFS, controlling tip/tilt modes in real
time at 1~kHz, allowed us to reduce the disturbances in air to 1e-3 lambda/D
rms, letting us achieve a contrast of 2.8e-7 between 1.2 and 2 lambda/D. Tests
are currently being performed to achieve the same or a better level of
correction in vacuum. With those results, and by comparing them to simulations,
we are able to deduce its performances on different coronagraphs - different
sizes of telescopes, inner working angles, contrasts, etc. - and therefore
study its contribution beyond EXCEDE.
