[Music]
Ira Thorpe: LISA Pathfinder is a mission led by the European Space Agency
to demonstrate technologies for a future space-based gravitational wave observatory.
We've just had a very historic event with the
successful detection of gravitational waves from the ground, and that was using these instruments called LIGO.
For detecting gravitational waves in space you need a slightly different kind of detector,
and the detector that we all are working towards has a name LISA, for Laser
Interferometer Space Antenna. So that's where we get the name LISA Pathfinder.
So basically it demonstrates some of the technologies that we will use on LISA
to eventually build a space-based gravitational wave detector. You're looking for these very
small distortions in space and time, and so you need to have some object
that you can use to reference space and time, basically something that's falling.
And any object in space, in principle it's sort of just falling, it's just feeling gravity.
But when you look at very exquisite detail you find there's other forces that are pushing
that object around, and so this technology called drag-free control was developed,
where the test mass actually sits inside the satellite, and the satellite's
flying around it like a flying shield. And so we needed to demonstrate this technology
and show that we could really place that test mass in absolutely perfect free fall,
and that's what we've done. The test was incredibly successful. The level that's been measured
you know, not only meets our requirement for LISA Pathfinder, but actually approaches
the requirement for doing the full-scale detector, for LISA, and so we're just absolutely thrilled
What that will allow us to do when we build the full scale detector is
detect gravitational waves from things like merging supermassive black holes at the edge of the
universe. What's shown
in the graph here is basically how imperfect this test mass
is in free fall. Right? So we'd like it to be perfect, it's not quite perfect,
and we're measuring the imperfection. This is directly what we measure with the
instrument and the very exciting thing is that it's far below the LISA Pathfinder
requirements. The first thing we noticed was at the very lowest frequencies
we had this increase in noise. This was actually due to the fact that the
spacecraft is jittering about in angle. And we can actually measure how the spacecraft jitters
and we can subtract it. The final thing we did was
we looked at the noise in this middle-frequency band here, and we determined that this is actually due to
some sort of subtle imperfections in the construction of the instrument.
And so we can fit these, and subtract them from the data, and we get down to this next line.
And this is exactly what we'd expect from a gravitational wave detector and tells
us that we're getting a very good understanding of our instrument.
The really exciting thing is if we place on this graph the requirement for the full-scale
detector, for the LISA detector. And you'll see that although we weren't these
requirements, we very nearly made these requirements. Here, essentially, we, you know,
turned it on out of the box and it just worked. If you were to take the performance of
LISA Pathfinder today and just build LISA with that same performance, you would get
the vast majority of the science that we've all been going after for all this time.
And, you know, this idea, the idea for LISA, the space-based gravitational wave detector, dates back
you know, more than 40 years, it's older than I am. And, you know, we haven't flown
the full mission yet, but we've flown a mission, you know, LISA Pathfinder, that's shown this is possible,
that you can actually do this. And, you know, some of these people that invested, you know, the past several
decades of their lives, you know, developing this mission and to see it work, it was just
totally inspiring. [Music]
[Music]
[Beeping]