Rosetta became a single…

Communication system on Rosetta was switched off today after 19 months since first in history soft landing on comet surface performed on 12 November 2014. 

One of the most recognized mission by ESA in recent years is definitely coming to its end. After announcing by European Space Agency on June 30, 2016, about setting date for the mission end for the Rosetta space probe to 30th September 2016, program entered into next phase of preparing to mission end. Its lander Philae was finally shut down. German space agency DLR announced on its blog about end of the Philae's mission on July 26, 2016. Today, punctually on 09:00 GMT main circuit of the Rosetta, Electrical Support System Processor Unit (ESS) was turned off.

Turning off communication system of Rosetta is important step of finalizing Rosetta/Philae mission before planned for 30 September 2016 controlled crashing Rosetta on 67P. Due the increasing distance from the Sun by 67P and Rosetta to 520 million kilometers in the end of July, solar arrays of the Rosetta will gradually provide less and less power. To provide enough electricity for Rosetta, to continue science experiments and taking detailed images of the 67P during descent, it is necessary to shut down everything what consumes energy and is not crucial for the mission.

Electrical Support System Processor Unit (ESS) is most crucial onboard device for Rosettae. It was designed in the cooperation between Maynooth University in Ireland and Space Technology Ireland Ltd (STIL) and it was responsible for transmitting, storing and coding commands for Philae; ESS was also receiving data from sensors and scientific payload of Philae. After shut down, Rosetta will no longer scan for signal from Philae and will use saved energy for charging onboard battery.

Whole Philae lander weight was 100 kg with 25 kg of payload mass. Its dimensions are 1 m x1 m x 0.8 m and it was power consumption was at 32 W. Trapezoidal in cross-section fuselage was covered with solar panels charging onboard battery. Front side of fuselage was place, where scientific sensors were installed. On the bottom, three arms were attached, each with drill for keeping Philae stable on surface of 67P. Scientific payload of the probe contained following devices:

  • APXS - Alpha Particle X-ray Spectrometer - performs analysis of the composition of the comet's surface.
  • CIVA - Comet Nucleus Infrared and Visible Analyzer - combination of the seven cameras (CCD with 1024 x 1024 pixels installed around lander every 60°), spectrometer and visible light microscope. Device was planned to analyze soil samples.
  • CONSERT - Comet Nucleus Sounding Experiment by Radiowave Transmission - device for research on internal structure of the comet with utilization of electromagnetic waves.
  • COSAC - Cometary Sampling and Composition - device for analysis of ground samples based on gas chromatograph and mass spectrometer.
  • MUPUS - Multi-Purpose Sensors for Surface and Sub-Surface Science - device for analyzing ground samples in terms of their mechanical and thermal properties.
  • Ptolemy – instrument for analyzing level of the stable isotopes inside comet's nucleus.
  • ROLIS - Rosetta Lander Imaging System - main high resolution CCD camera of the Philae providing stereo panoramic images (based on 1024 x1024 CCD unit).
  • ROMAP - Rosetta Lander Magnetometer and Plasma Monitor - magnetometer and plasma sensor for analyzing of nucleus of 67P
  • SD2 - Sampling, Drilling and Distribution System - key scientific device, designed to take soil samples from depth of 23 cm and transfer them to Ptolemy, COSAC and CIVA for further analysis. It was combined with oven for heating frozen samples. Device was designed under supervision of ASI with Selex ES S.p.A, Eni S.p.A., Media Lario and Dallara.
  • SESAME - Surface Electric Sounding and Acoustic Monitoring Experiments - instrument for measuring dust dynamics, structure of surface and electrical characteristic of outer layers of the comet.

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On picture above: Philae and Rosetta before deploying.

Philae lander was launched onboard of Rosetta on March 2, 2004 on atop of Ariane 5 rocket from Guiana Space Center. After twelve years of space journey, Rosetta and Philae reached 67P on August 6, 2014 and performed deployment of the Philae landed on November 12, 2014 from altitude of 29 km over 67P surface. Probe softly landed on 67P and started to send data transmission to Rosetta. Despite the fact that landing was correct, Philae touched surface of the comet in place where it remained in the shadow. Philae was unable to charge onboard battery and after 48 hours communication was terminated due the lack of power. Philae was shut down on 15 November, 2014 at 00:36 GMT. Surprisingly on 13 June 2015 at 20:28 GMT, Philae sent data to Rosetta. Next time contact with Philae was resumed on June 19, 2015 and during next week nine transmissions to Rosetta were confirmed. Unfortunately any commands sent to Philae via Rosetta from ground Control Station failed to be executed correctly and lander was not able to perform its main scientific experiment: drilling into surface of the comet to perform analysis of its composition. Since July 9, 2015, when Philae was last time able to establish communication with Rosetta, until January 2016 no communication have been established and ESA started to consider lander as lost.

Sources:

http://www.dlr.de/rd/Portaldata/28/Resources/dokumente/rx/Philae_Lander_FactSheets.pdf
http://blogs.esa.int/rosetta/2016/07/26/farewell-silent-philae/
https://www.maynoothuniversity.ie/news-events/maynooth-university-scientists-play-key-role-historic-rosetta-mission