Rosetta blog: Philae wake-up triggers heated planning

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The receipt of signals from Rosetta’s Philae lander on 13 Jun after 211 days of hibernation noted a start of heated activity. In coordination with a goal partners, ESA teams are operative to juggle Rosetta’s moody digest to assistance with renewed lander scholarship investigations. 

Philae has woken adult after 7 months in hibernation on Comet 67P/Churyumov–Gerasimenko. Hidden by shadows, Philae close down on 15 Nov 2014 during 00:36 GMT after completing a categorical scholarship operations method on a comet when a primary battery lapsed as approaching after about 60 hours.

This picture was taken by Rosetta’s NavCam during 19:38 GMT on 13 Jun 2015, shortly before Philae’s wake-up vigilance was received. The signals were relayed by a Rosetta orbiter and perceived during ESA's European Space Operations Centre in Darmstadt during 20:28 GMT.  The picture was taken from a stretch of 201 km from a centre of Comet 67P/Churyumov–Gerasimenko and measures 17.5 km across. The picture scale is 17.1 m/pixel. The comet is orientated with a tiny lobe towards a right, with a vast basin famous as Hatmehit visible. Philae is suspicion to be resting only outward a rim, towards a tip right in this image.  Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0

This picture was taken by Rosetta’s NavCam during 19:38 GMT on 13 Jun 2015, shortly before Philae’s wake-up vigilance was received. The signals were relayed by a Rosetta orbiter and perceived during ESA’s European Space Operations Centre in Darmstadt during 20:28 GMT.
The picture was taken from a stretch of 201 km from a centre of Comet 67P/Churyumov–Gerasimenko and measures 17.5 km across. The picture scale is 17.1 m/pixel. The comet is orientated with a tiny lobe towards a right, with a vast basin famous as Hatmehit visible. Philae is suspicion to be resting only outward a rim, towards a tip right in this image.
Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0

Since Mar 2015, when Philae’s environmental conditions started to urge with aloft aspect temperatures and improved illumination, a orbiter’s receiver had been incited on intermittently to listen for signals from a lander when a orbital geometry was suspicion to be optimum.

On a dusk of 13 June, a diseased though plain radio couple between Rosetta and a lander was finally dynamic for 85 seconds. More than 300 ‘packets’ – 663 kbits – of lander housekeeping telemetry were received. This information had been stored on house during an as-yet-to-be dynamic time in a past, as most as several days to a few weeks, so does not indispensably simulate a lander’s stream status.

Rosetta afterwards relayed a vigilance to ESA’s European Space Operations Centre, ESOC, in Darmstadt, Germany, during 20:28 GMT.

“We are still examining a housekeeping information during a Lander Control Centre in a DLR German Aerospace Center’s investiture in Cologne, though we can already tell that all lander subsystems are operative nominally, with no apparent plunge after some-more than half a year stealing out on a comet’s solidified surface,” says DLR’s Stephan Ulamec, Philae Lander Project Manager.

A second, smaller detonate of lander information was perceived on Sunday, 14 June, during about 21:26 GMT, durability only a few seconds. These information were reliable to give a stream status, display a lander’s inner feverishness had already risen to –5ºC.

Philae’s memory has stored over 8000 packets of additional standing data, though it is misleading from when in new days they were recorded.

This picture from Rosetta’s OSIRIS narrow-angle camera shows a Philae lander during 10:23 GMT (onboard booster time) on 12 November, roughly dual hours after separation. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

This picture from Rosetta’s OSIRIS narrow-angle camera shows a Philae lander during 10:23 GMT (onboard booster time) on 12 November, roughly dual hours after separation.
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Here comes a Sun

Engineers during a Lander Control Centre have dynamic that Philae is already being unprotected to sufficient object to feverishness it to an excusable handling feverishness and to beget electricity.

“Power levels boost during a internal ‘comet day’ – a partial of a about-12 hour comet revolution when Philae is in object – from 13 W during comet morning to above 24 W,” records ESA’s Patrick Martin, Rosetta Mission Manager. “It needs during slightest 19 W to switch on a transmitter.”

The telemetry downloaded lonesome a lander’s standing for a full night–day cycle of a comet, that is assisting belligerent teams to know how a Sun is resplendent on a lander. The solar panels seem to be receiving energy for over 135 mins in any enlightenment period.

“While a information we have is really preliminary, it appears that a lander is in as good a condition as we could have hoped,” says Dr Ulamec.

The charge during hand

The categorical charge now for all a goal partners – ESA for Rosetta operations and DLR and France’s CNES space group for lander operations and science, respectively – is to settle how to optimise Rosetta’s circuit so as to promote hit and capacitate new scholarship investigations.

It is believed that there is sufficient energy now being generated to concede some scholarship measurements during a time Philae is illuminated, with initial activities focusing on low-power measurements. This initial proviso would also expected embody measurements that did not formerly beget scholarship in November.

However, a goal teams initial contingency settle a some-more strong couple between Rosetta and Philae before uploading a initial collection of scholarship operations commands.

The peculiarity of a communication couple is also presumably associated to a arena Rosetta is drifting and a course it adopts.

Artist sense of Rosetta and Philae during Comet 67P/C-G (not to scale). Credits: ESA/ATG medialab; Comet image: ESA/Rosetta/Navcam

Artist sense of Rosetta and Philae during Comet 67P/C-G (not to scale). Credits: ESA/ATG medialab; Comet image: ESA/Rosetta/Navcam

Optimising an circuit 305 million km away

Currently, Rosetta practice dual probable communication slots per 24 hours – once per 12-hour comet rotation.

Until 23:35 GMT on Tuesday, 16 June, Rosetta will be drifting an circuit set by already-uploaded commands on a terminator – a craft between comet day and night – relocating out from about 200 km to 235 km altitude.

This circuit is not optimised for lander communication, so longer durations of hit might not be probable until a arena has been changed.

“With work finished by a moody dynamics and operations group during ESOC and formed on heated formulation being conducted with a goal partners today, a new circuit will be devised that ensures best lander communications commencement with a subsequent authority upload after tonight,” says Paolo Ferri, ESA’s Head of Mission Operations.

This new circuit will embody an already-planned rebate of stretch from a nucleus, down to 180 km contra 200 km, and ‘nadir pointing’ – invariably indicating Rosetta’s communications section during a comet. In a entrance days, a orbiter might also be changed closer to a comet, but compromising a reserve of a spacecraft, to assistance communications.

The new circuit will be flown by Rosetta starting after 23:25 GMT on 16 Jun until 19 June, aiming to capacitate some-more and longer contacts with Philae, generally towards a finish of this period.

Ready to conflict quickly

Establishing a unchanging and expected settlement of contacts is a exigency for behaving a finish comment of a lander’s standing and for formulation scholarship operations.

“If we conduct to grasp and say a expected hit pattern,” continues Paolo Ferri, “the lander teams can digest a plan for a new method of systematic operations.

“Regardless, we will stay really stretchable and be prepared to conflict quickly. It’s transparent this implausible goal continues to kindle and plea us, building in ways we could never have predicted.”

As a bonus, any operation of Philae’s instruments adult to or by perihelion on 13 Aug – a comet’s closest indicate to a Sun along a circuit – will concede in-situ investigate of a comet during a rise activity.

Had Philae landed during a designed site, during Agilkia in Nov 2014, a goal would expected have finished in Mar since of a aloft temperatures of that plcae as solar enlightenment increased.

Rosetta is an ESA goal with contributions from a Member States and NASA. Rosetta’s Philae lander is contributed by a consortium led by DLR, MPS, CNES and ASI.

Source: Rosetta blog