PRIMA, the instrument for Phase Referenced Imaging and Micro-arcsecond Astrometry, will implement the dual-feed capability at the ESO Very Large Telescope Interferometer (VLTI). In order to implement the Micro-arcsecond Astrometry and conduct an astrometric Exoplanet Search program with PRIma (ESPRI), MPIA together with the Landessternwarte Heidelberg and the Geneva Observatory have formed a consortium to build Differential Delay Lines (DDLs) for PRIMA and to develop the astrometric operation and software tools.

ESPRI will astrometrically measure the reflex motion of the star. For nearby stars it will be more sensitive to planets in Earth-like orbits than radial velocity surveys. It allows planet masses to be determined without the sin(i) ambiguity, and can detect planets in face-on orbits.

The accurate differential-astrometry measurements will be achieved by simultaneously observing the target and a reference star separated by a small angle, using the dual-feed PRIMA facility at the VLTI interferometer. Further details of this approach for detecting extra-solar planets can be found in the Method section of this website.

The principle hardware contributions to PRIMA from MPIA are the cats-eye retro-reflectors for the differential delay lines (DDLs). MPIA has also had a major role in the development of the science case, observing strategy, observation planning, error budget and software for the ESPRI program.

Principle project milestones

• BDR — Baseline Design Review, September 2003. During this review, which was internal to the Consortium, the baseline design to be proposed to ESO (Technical and AOS Proposal) was reviewed and preliminary specifications were released. The scientific objectives were summarized in the Scientific Proposal. Also, the first issues of the Management Plan, Project Plan and Financial Plan were presented to the Partners.
• KO — Kick-Off, 23rd June 2004. The project Kick-Off involved the signing of an agreement between ESO and the Consortium. It defined the time T0 for the project schedule.
• PDR — Preliminary Design Review, 27th June 2005. During the PDR every WP manager presented his work package and the design of the corresponding subsystem or software package. The design and the interfaces were reviewed jointly by ESO and the Consortium. After successful evaluation, ESO granted authorization to start with the detailed design phase.
• FDR — Final Design Review, 3rd April 2007. At the FDR, WP managers presented their work packages. The detailed design was passed jointly by ESO and Obs. de Geneva.
• IRR — Integration Readiness Review, February 2008. This review has taken place for the AOS and the DDLs just before the integration started, since otherwise the period between FDR and PAE would have been too long. The idea would be to ensure that all components, subsystems and SW modules are ready and tested before starting the integration.
• PAE — Provisional Acceptance Europe, June 2008. The PAE took place after successful integration and test of the AOS and of the instrument in Europe. The AOS and the DDL review can be separated. The DDL review took place shortly before the DDLs left for Paranal. The review helped to verify whether the performances, safety and reliability requirements are met in laboratory, and to decide whether the instrument is mature enough for Paranal operation.
• PAC — Provisional Acceptance Chile. The PAC shall take place after astrometry commissioning in Paranal. ESO will grant the Provisional Acceptance of the project, provided that the technical and operation requirements are fulfilled.
• FAC — Final Acceptance Chile. The FAC for the AOS shall take place after 3 years of operation. ESO will then grant the Final Acceptance of the project.