Subject: Philae Lander comes out of Hibernation
From: Alex Kemp
Date: Sunday, 14 June 2015 21:43:01 +0100
To: Oliver Kemp, Micaela Kemp, Liisa Kemp, Davin Kemp

15 November 2014 at 0:15 UTC: Philae shut down (into hibernation)
12 March 2015: Rosetta orbiter communication unit turned on to listen out for the lander
13 June 2015 at 20:28 UTC: Philae communicates to ESA, Darmstadt via Rosetta that it has woken up

(UTC=Universal Coordinated Time == same as GMT)
(UK is currently UTC 01:00 due to Summer Time)
(Darmstadt is currently CEST == UTC 02:00)

Naturally, Philae tweeted that it was awake:

Tweet from Philae Lander
Tweet from Philae Lander
Tweet from ESA Rosetta Mission
Tweet from ESA Rosetta Mission

“Waking up” is a complicated business for Philae:

  1. The lander needs to be at −45 °C or above to reboot
    (currently working temp is −35 °C)
    (it was −160 °C on the comet last November)
    Power from the solar panels are sent to heaters until min temp reached.
  2. The batteries can only recharge when above 0°C
    comet 67P/Churyumov-Gerasimenko rotates once every 12.4-hours
    Philae has sunlight for just 1.3 hours (80 mins) of each cycle.
    Philae needed about 17 Watts to wake up and say “hello”.
    It is currently getting 24 watts.

It looks like Philae has been awake for a while, but unable to contact it’s mother ship Rosetta. When out of contact it is designed to place gathered data into non-volatile storage and, after contact had been made, Philae sent 300 data packets & reported another 8,000 waiting to be sent.

ESA still does not know exactly where the pesky lander landed. As radio communication continues that will also eventually be answered.

Alex Kemp