Planck and Being Human

On Saturday 19th October the instruments and cooling systems on the European Space Agency’s Planck spacecraft were switched off, marking the end of the scientific part of the Planck mission, after about four years of mapping the cosmic microwave background.  Later, a piece of software was uploaded that would prevent  the spacecraft systems being  accidentally switched on again after being switched off and the transmitter from causing interference with any future probes.  Planck is already “parked” indefinitely in a what is called a “disposal” orbit, far from the Earth-Moon system, having been nudged off its perch at the 2nd Lagrangian Point (L2) in August by a complicated series of manoeuvres. On October 21st the spacecraft’s thrusters were fired to burn up the last of its fuel, an important aspect of rendering the spacecraft inert, as required by ESA’s space debris mitigation guidelines.

These preliminaries having been completed, today, at 12.00 GMT,  a final instruction will be transmitted to the spacecraft  to close it down permanently; thereafter Planck will circle the Sun as a silent memorial to the stunning success it achieved when active. I’m sure all those who worked on the Planck mission will pause as the final shutdown command is given and ponder the lonely future  of the spacecraft that had supplied so much interesting data.

But although this will be the end of the Planck mission, it is by no means the end of the Planck Era. Vast amounts of data still need to be fully analysed and key science results are still in the pipeline,  relating in particular to the polarization of the microwave background radiation. Moreover, the numerous maps, catalogues and other data products will be a priceless legacy to this generation, and no doubt many future generations, of scientists.

The fate of Planck illustrates two contrasting aspects of the human experience. On the one hand, there’s the fragility of our existence in a cosmos too vast for us to comprehend. Like the defunct spacecraft, our Earth too circles this little Sun of ours in a precarious orbit while the rest of the Universe – with its countless billion upon billion of other suns – carries on, oblivious to our very existence. Planck makes us painfully aware of our own insignificance.

But on the other hand there’s the sense of fulfillment, and even of joy, at finding things out. We may have puny monkey brains and many things are likely to remain forever beyond our mental grasp, but trying to figure things out is one of the things that defines us as human.  Experiments like Planck (and, for that matter, the Large Hadron Collider) are not the wasteful extravagance some people claim them to be. We need them not just for the sake of science, but to remind us of our common humanity.

UPDATE: And now, from ESA, confirmation that Planck has received its last command. Goodbye, and enjoy your retirement!

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