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Accomazzo A.,European Space Agency | Ferri P.,ESOC ESA | Lodiot S.,ESOC ESA | Pellon-Bailon J.-L.,ESOC ESA | And 5 more authors.
Acta Astronautica | Year: 2017

The International Rosetta Mission was launched on 2nd March 2004 on its 10 year journey to rendezvous with comet 67P Churyumov-Gerasimenko. Rosetta performed comet orbit insertion on the 6th of August 2014, after which it characterised the nucleus and orbited it at altitudes as low as a few kilometres. In November 2014 Rosetta delivered the lander Philae to perform the first soft landing ever on the surface of a comet. After this critical operation, Rosetta began the escort phase of the comet in its journey in the Solar System heading to the perihelion, reached in August 2015. Originally foreseen till the end of 2015, the mission was extended for another nine months to follow the comet on its outbound arc of the orbit. In view of the acquired experience and of the approaching end of mission the spacecraft was flown at much closer distances from the nucleus so that the scientific instruments had the chance to perform unique measurements. Following this phase of very close orbits, on the 30th of September 2016 Rosetta was set on a collision course trajectory with the comet to terminate the mission with a controlled impact. This paper describes the details of the extended mission phase and the issues encountered during these months. It also includes the changes implemented on the spacecraft and in the operations concept to optimise the remaining mission time. The paper also includes the lessons learned from this unique and complex mission phase. © 2017

Accomazzo A.,European Space Agency | Ferri P.,ESOC ESA | Lodiot S.,ESOC ESA | Pellon-Bailon J.-L.,ESOC ESA | And 6 more authors.
Acta Astronautica | Year: 2015

The International Rosetta Mission was launched on 2nd March 2004 on its 10 year journey to comet Churyumov-Gerasimenko and has reached it early August 2014; it will now orbit it for about 1.5 years down to distances of a few kilometres and has delivered the Lander Philae onto its surface. Following the exit in January 2014 from a 2.5 years hibernation period, necessary due to the large heliocentric distances reached by the solar-powered spacecraft, which prevented full operation of the on-board electrical systems, Rosetta conducted the delicate approach phase during which it slowly discovered its unexpected irregular shape. The spacecraft is now flying in close proximity of the comet and has begun its main science phase. The comet has been characterised to the level necessary to perform a proper orbit insertion and proceed with the global mapping and close observation phases. During this phase the landing site for Philae has been selected with all operations focusing on this extremely delicate and risky mission phase. The mission has been conducted according to plan and the planning and operations concepts defined have revealed to be adequate for the environment encountered during the early comet phases. The performance of the spacecraft and of the whole operations teams have been very good; all the tools and processes developed to characterise and model the environment revealed to be adequate and provided results that are fully in line with the needs. This paper describes the flight operations conducted till November 2014, the results and the performance of the mission from an operations point of view, and some of the details of the landing phase. Finally it also addresses the lessons learned that can be drawn after this initial phase of comet operations. © 2015 IAA. Published by Elsevier Ltd. All rights reserved.

Giannini A.,University of Pavia | Pelorossi F.,ESOC ESA | Pasian M.,University of Pavia | Bozzi M.,University of Pavia | And 3 more authors.
IEEE Antennas and Propagation Magazine | Year: 2015

This paper describes the most recent improvements for the upcoming upgrade to telemetry, tracking and command (TT&C) capabilities for the Sardinia Radio Telescope (SRT), a 64-m antenna tailored for radio-astronomical observations of cosmic radio sources located in the outer space. Due to the TT&C improvement, the SRT will represent one of the Europe's main establishments for the support of present and future deep space missions. The first part of this paper is dedicated to the Gaussian Beam synthesis of the SRT feeding system, called beam waveguide, fashioned to maximize the antenna illumination and spillover efficiency. The best design parameters have been retrieved through a rapid and efficient optimization analysis and verified by means of physical optics simulations. In accordance with the obtained results from the Gaussian formulation, further in-depth studies have been undertaken in order to investigate a technique able to overcome the so-called beam squint issue, a typical drawback that occurs during the tracking process of active spacecrafts. The proposed approach manages to automatically attain and quickly the best antenna beam steering strategy to correct the squint issue by means of a field-matching algorithm. Finally, this paper reports the analyses developed for electromagnetic hazard predictions, which shall be carefully taken into consideration for the safety of personnel working close to the high-power radiating installations and for preventing the astronomical receivers located near the Prime and the Gregorian foci from being damaged when the antenna is transmitting. © 2015 IEEE.

Di Giulio M.,ESOC ESA
European Space Agency, (Special Publication) ESA SP | Year: 2015

Cross Support Transfer Services (CSTS) are standardized services to allow interoperability between different space agencies for mission cross support. A service user from one agency can use services that are provided from the ground station belonging to another agency. The CCSDS Space Link Extension (SLE) services for delivery of spacecraft telemetry and telecommand between ground stations and control centers are very successful examples for these kinds of services, and have been deployed by almost all space agencies. The CCSDS CSTS Standardization Working Group is about to complete the work on a CCSDS Cross Support Transfer Service Specification Framework. This framework shall facilitate the definition of new cross support services. New services can be composed of already existing or derived procedures and operations. The modular nature of the framework shall also support the implementation of these new services by increasing the options for reusing software components for several services. This paper gives a brief overview of the work of the CCSDS CSTS Standardization Working Group and introduces the concepts of the CSTS Specification Framework and of Services build using such Framework. In order to get any CCSDS recommendation to be published, prototype(s) must be developed, to proof the concepts. This paper will also introduce the prototype developed by the participating Agencies. In particular it will address the ESA-implemented prototype of the Framework (the CSTS Development Kit) based on reuse of the existing SLE API.

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