The objectives of this project are the study and development of a new version of the InfraRed Earth Sensor IRES based on the extensive in flight experience of previous IRES NE ones.
The main changes are aimed at an overall cost reduction and, taking advantage of technological innovations, maintaining the same performances of the previous version:
The contract will have, as starting point, the experience gained from the IRES NE Earth Sensor, which is the current production with more than 80 units produced up to now for several TLC programmes (SATELCOM, SPACEBUS 3000 and SPACEBUS 4000, AMOS, DFH Series).
The sensor main characteristics are:
The new development IRES N2 is mainly addressed at the electronic section: in particular, bolometer detectors are replaced by pyroelectric ones.
An extensive use of SMD components is adopted, maintaining the same electronic architecture of the IRES NE; exotic and obsolete components are removed, as well as USA components subjected to ITAR restrictions.
The opto-mechanical part remains unchanged in its peculiar items, like the indefinite life scanning mechanism and the IR telescope, while an optimisation of the housing is put in place to allocate the new electronic layout and improve production processes.
The strong need to maintain the telecommunication and constellation commercial market defined the IRES N2 drivers as the significant reduction of the overall recurring cost of the sensor, both in terms of material and manpower, maintaining accuracy and lifetime of the preceding IRES generations.
The use of ITAR Free components, together with the removal of exotic, obsolete and long lead EEE components reduces delivery times and increases the sensor exportability
The IRES N2 is a two axis infra-red Earth horizon sensor for accurate measurement of pitch and roll attitude angles with respect to the Earth disk center, used in three-axes stabilised spacecrafts.
The operating principle is based on electro-mechanical modulation of the Earth radiation in the 14-16Â¼m band. Four IR detectors scan the Earth horizon by the means of a frictionless scanning mechanism suspended by flexural pivots. The Space/Earth and Earth/Space transitions are detected and converted into angular data by an incremental encoder.
The system architecture is divided into the following main blocks:
The mechanical hardware consists of an optical head and the relevant processing electronics both contained in the same main housing coated by Alodyne.
The project is divided into four main phases:
The first phases of the project were related to the IRES re-design (pyroelectric detectors and electronics upgrade). The subsequent phases of the project were related to the manufacturing of an EQM unit and its full qualification. In parallel the evaluation of the pyroelectric detectors has been carried out.
The following scheduled key milestones have been completed:
All the activities were concluded in November 2006.
The full on ground qualification has been reached and the sensor is ready for the market both for GEO and MEO applications.
The unit has been qualified (DS32, 50VDC power bus) at the following environmental conditions:
The evaluation campaign on the pyroelectric detectors has been successfully completed demonstrating the detectors suitability for flight use in long lifetime space applications.
The IRES N2 was chosen as the Earth Sensor unit in the Galileo IOV programme and the FMs will be delivered in 2008.