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We describe the activities performed by SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and cube/microsat Characterization Facilities Laboratory) of INFN-LNF for the thermo-optical vacuum testing activity of a IRNSS (Indian Regional Navigation Satellite System) LRA (Laser Retroreflector Array), under contract for ISRO-LEOS. To our knowledge, this is the first publication on the characterization of the optical performance of an LRA operating at about 36,000 km altitude (typical of regional GNSS segments, namely QZSS, COMPASS-G) executed in fully representative, carefully lab-simulated space conditions. In particular, this is the only such publication concerning IRNSS. Since laser ranging to its altitude is more challenging than to GNSS altitudes (from about 19,100 km for GLONASS to about 23,200 km for Galileo), comparative measurements were long awaited by ILRS (International Laser Ranging Service) and we present measurements of the absolute laser return to ground stations of the ILRS in terms of lidar OCS (Optical Cross Section) at the IRNSS relevant value of velocity aberration, in turn derived from measurements of the full FFDP (Far Field Diffraction Pattern) over a very large range of velocity aberrations. These measurements were acquired: (i) on a full-size qualification model of a IRNSS CCR (Cube Corner Retroreflector) LRA that ISRO-LEOS provided to INFN-LNF; (ii) during the lab-simulation of a 1/4 orbit segment, in which the LRA CCRs are exposed to the perturbation of the sun heat at varying angles, from grazing incidence (90° with respect to the direction perpendicular to the plane of array), up to the perpendicular to the LRA, with a same time variation consistent with the actual space orbit. In this 1/4 orbit condition, the LRA experiences potentially large thermal degradations of the OCS, depending on the detailed thermal and mechanical design of the LRA. Since all GNSS constellations have different LRA designs or configurations, this is another reason of the interest in the laboratory optical performance of the IRNSS designs. In fact, we tested two different IRNSS LRA configurations, without and with an auxiliary cover. The latter of the configurations is designed to give a somewhat increased performance. We also measured FFDPs and OCS: (1) in-air isothermal conditions (thus obtaining the LRA nominal performance); (2) in space conditions at a low, stationary value of the LRA bulk temperature; (3) in space conditions at a high, stationary value of the LRA bulk temperature ( Figs. S1–S18 , available in the online supplementary material for this paper). In all these three cases, we measured FFDPs and OCS at the following laser incidence angles: (a) normal to the LRA plane; (b) +9° to the normal to the LRA plane; (c) −9° to the normal to the LRA plane. This is the first time, to our knowledge, that the measurements (not simulations) at ±9° (values requested by ISRO-LEOS) are published for GNSS LRAs. Finally, we point out that we measured full-FFDP and OCS of single CCRs, for maximum diagnostic value and performance validation at subelement level. For all these reasons, the articulate and variate set of tests of the IRNSS LRA reported in this paper is unique.

During Summer 2015 the SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and cube/microsat Characterization Facilities Laboratory, www.lnf.infn.it/esperimenti/etrusco) Team of INFN-LNF, with support by ASI, carried out an intense activity of final design, manufacturing and testing in order to construct, space qualify and finally integrate INRRI-EDM/2016 on ESA’s ExoMars EDM spacecraft (also dubbed ‘Schiaparelli’), which was successfully launched on March 14, 2016. INRRI (INstrument for landing-Roving laser Retroreflector Investigation) for the EDM (Entry descent and landing Demonstration Module) 2016 mission is a compact, lightweight, passive, maintenance-free array of eight cube corner laser retroreflectors fixed to an aluminum alloy frame through the use of silicon rubber suitable for space applications. INRRI was installed on the top panel of the EDM Central Bay on October 14, 2015. It will enable the EDM to be laser-located from Mars orbiters, through laser ranging and altimetry, lidar atmospheric observations from orbit, laser flashes emitted by orbiters, and lasercom. One or all of the above means of observation can be supported by INRRI when there is an active, laser-equipped orbiter, especially after EDM end-of-life and for a long time. INRRI goals will cover science (Mars geodesy/geophysics, future Mars test of General Relativity, GR), technology and exploration. Concerning the latter two, INRRI will support mars-georeferencing of the EDM landing site, support potential precision lidar-based landing next to the EDM, support test & diagnostics of lasercom for data exchange among Mars orbit, Mars surface and Earth, and it will be a precursor for additional Mars surface retroreflectors, for example on exploration rovers. This paper describes in detail our innovative payload, hopefully the very first to be deployed safely with the lander Schiaparelli on the Mars surface, and its space qualification for the ExoMars EDM 2016 mission. Despite the fate of the Schiaparelli landing, which is still under the investigation of ESA and the industry, this paper remains a valuable reference for next INRRI-like laser retroreflectors arrays.

The Galileo constellation is a space research and development program of the European Union to help navigate users all over the world. The Galileo IOV (In-Orbit Validation) are the first test satellites of the Galileo constellation and carry satellite laser retroreflectors as part of their payload systems for precision orbit determination and performance assessment. INFN-LNF SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and Cube/microsat Characterization Facilities Laboratory) has been performing tests on a sample of the laser array segment under the Thermo-optical vacuum testing of Galileo IOV laser retro-reflectors of Galileo IOV LRA project, as defined in ESA-INFN Contract No. 4000108617/13/NL/PA. We will present the results of FFDP (Far Field Diffraction Pattern) and thermal relaxation times measurements in relevant space conditions of Galileo IOV CCRs (Cube Corner Retroreflectors) provided by ESA-ESTEC. A reference for the performance of laser ranging on Galileo satellites is the FFDP of a retroreflector in its design specifications and a Galileo retroreflector, in air and isothermal conditions, should have a minimum return intensity within the range [ 0.55 × 10 6 m 2 – 2.14 × 10 6 m 2 ] (ESA-INFN, 2013). Measurements, performed in SCF_Lab facility, demonstrated that the 7 Galileo IOV laser retroreflectors under test were compliant with design performance expectations (Porcelli et al., 2015). The kind of tests carried out for this activity are the first performed on spare Galileo IOV hardware, made available after the launch of the four Galileo IOV satellites (2011 and 2012), which were the operational core of the constellation. The characterisation of the retroreflectors against their design requirements is important because LRAs (Laser Retroreflector Arrays) will be flown on all Galileo satellites.

The SCF_Lab (Satellite/lunar/gnss laser ranging and altimetry Characterization Facility Laboratory) of INFNLNF is designed to cover virtually LRAs (Laser Retroreflector Arrays) of CCRs (Cube Corner Retroreflectors) for missions in the whole solar system, with a modular organization of its instrumentation, two redundant SCF (SCF_Lab Characterization Facilities), and an evolutionary measurement approach, including customization and potentially upgrade on-demand. See http://www.lnf.infn.it/esperimenti/etrusco/ for a general description.

We developed advances laser retroreflectors for solar system exploration, geodesy and for precision test of General Relativity (GR) and new gravitational physics: a micro-reflector array (INRRI, Instrument for landing-Roving laser Retroreflectors Investigations), a midsize reflector array for the European Earth Observation (EO) program, Copernicus (CORA, COpernicus laser Retroreflector Array), a large, single-retroreflector (MoonLIGHT, Moon Laser Instrumentation for General relativity High accuracy Tests). These laser retroreflectors will be fully characterized at the SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry Cube/microsat Characterization Facilities Laboratory), a unique and dedicated infrastructure of INFN-LNF (www.lnf.infn.it/esperimenti/etrusco/). Our research program foresees several activities: 1) Developing and characterizing the mentioned laser retroreflector devices to determine landing accuracy, rover positioning during exploration and planetary/Moon’s surface georeferencing. These devices will be passive, laser wavelength- independent, long-lived reference point. INRRI will enable the performance of full-column measurement of trace species in the Mars atmosphere by future space-borne lidars. These measurements will be complementary to highly localized measurements made by gas sampling techniques on the Rover or by laser back-scattering lidar techniques on future orbiters and/or from the surface. INRRI will also support laser and quantum communications, carried out among future Mars Orbiters and Mars Rovers. This will be possible also because the INRRI laser retroreflectors will be metal back-coated and, therefore, will not change the photon polarization. The added value of INRRI is its low mass, compact size, zero maintenance and its usefulness for any future laser altimetry, ranging, communications, atmospheric lidar capable Mars orbiter, for virtually decades after the end of the Mars surface mission, like the Apollo and Lunokhod lunar laser retroreflectors. MoonLIGHT and INRRI are proposed for landings on the Moon (two Google Lunar X Prize Missions, namely Moon Express; Russia’s Luna-27 mission, as well as others under consideration/negotia- tion, also with the help of ASI, ESA and other partnerships); 2) Precision tests of GR with LLR to MoonLIGHT reflectors. Development of new fundamental gravity physics models and study of experimental constraints to these models use also laser ranging and laser reflectors throughout the solar system: extension of general relativity to include Spacetime Torsion, Non-Minimal Coupling between matter and curvature (so-called “ ” theories, or NMC gravity); 3) Extension of program to: Mars, Phobos and Deimos, Jupiter and Saturn icy/rocky moons, Near Earth Asteroids.

Over the past 40 years, Lunar Laser Ranging (LLR, developed by the Univ. of Maryland (PI) and INFN-LNF (Co-PI)) to the Apollo Cube Corner Retroreflector (CCR) arrays have supplied almost all the significant tests of General Relativity (Currie et al., 2009 [12] ). LLR can evaluate the PPN (Post Newtonian Parameters), addressing this way both the possible changes in the gravitational constant and the self-energy properties of the gravitational field. In addition, the LLR has provided significant information on the composition and origin of the Moon. This is the only Apollo experiment that is still in operation. Initially the Apollo LLR arrays contributed a negligible fraction of the ranging error budget. Over the decades, the ranging capabilities of the ground stations have improved by more than two orders of magnitude. Now, because of the lunar librations, the existing Apollo retroreflector arrays contribute a significant fraction of the limiting errors in the range measurements. We built a new experimental apparatus (the ‘Satellite/Lunar Laser Ranging Characterization Facility’, SCF) and created a new test procedure (the SCF-Test) to characterize and model the detailed thermal behavior and the optical performance of cube corner laser retroreflectors in space for industrial and scientific applications (Dell'Agnello et al., 2011 [13] ). Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of the SLR retroreflector payload under thermal conditions produced with a close-match solar simulator. The apparatus includes infrared cameras for non-invasive thermometry, thermal control and real-time movement of the payload to experimentally simulate satellite orientation on orbit with respect to both solar illumination and laser interrogation beams. These unique capabilities provide experimental validation of the space segment for SLR and Lunar Laser Ranging (LLR). The primary goal of these innovative tools is to provide critical design and diagnostic capabilities for Satellite Laser Ranging (SLR) to Galileo and other GNSS (Global Navigation Satellite System) constellations. Implementation of new retroreflector designs being studied will help to improve GNSS orbits, which will then increase the accuracy, stability, and distribution of the International Terrestrial Reference Frame (ITRF) [4] , to provide better definition of the geocenter (origin) and the scale (length unit). The SCF is also actively used to develop, validate and optimize the second generation LLR arrays for precision gravity and lunar science measurements to be performed with robotic missions of the International Lunar Network in which NASA and ASI participate (ILN). The capability will allow us to optimize the design of GNSS laser retroreflector payloads to maximize ranging efficiency, to improve signal-to-noise conditions in daylight and to provide pre-launch validation of retroreflector performance under laboratory-simulated space conditions. For the MAGIA lunar orbiter Phase A study funded by ASI (Dell'Agnello et al., 2010 [14] ), we studied fundamental physics and absolute positioning metrology experiments, to improve test of the gravitational redshift in the Earth–Moon system predicted by General Relativity and a precursor test of our second generation LLR payload.

MAGIA is a mission approved by the Italian Space Agency (ASI) for Phase A study. Using a single large-diameter laser retroreflector, a large laser retroreflector array and an atomic clock onboard MAGIA we propose to perform several fundamental physics and absolute positioning metrology experiments: VESPUCCI, an improved test of the gravitational redshift in the Earth–Moon system predicted by General Relativity; MoonLIGHT-P, a precursor test of a second generation Lunar Laser Ranging (LLR) payload for precision gravity and lunar science measurements under development for NASA, ASI and robotic missions of the proposed International Lunar Network (ILN); Selenocenter (the center of mass of the Moon), the determination of the position of the Moon center of mass with respect to the International Terrestrial Reference Frame/System (ITRF/ITRS); this will be compared to the one from Apollo and Lunokhod retroreflectors on the surface; MapRef, the absolute referencing of MAGIA’s lunar altimetry, gravity and geochemical maps with respect to the ITRF/ITRS. The absolute positioning of MAGIA will be achieved thanks to: (1) the laboratory characterization of the retroreflector performance at INFN-LNF; (2) the precision tracking by the International Laser Ranging Service (ILRS), which gives two fundamental contributions to the ITRF/ITRS, i.e. the metrological definition of the geocenter (the Earth center of mass) and of the scale of length; (3) the radio science and accelerometer payloads; (4) support by the ASI Space Geodesy Center in Matera, Italy. Future ILN geodetic nodes equipped with MoonLIGHT and the Apollo/Lunokhod retroreflectors will become the first realization of the International Moon Reference Frame (IMRF), the lunar analog of the ITRF.

The SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and Cube/microsat Characterization Facilities Laboratory) is a brand new ISO 7 Clean Room, dedicated to design, characterization and modelling of the space segment of Satellite Laser Ranging (SLR), Lunar Laser Ranging (LLR) and Planetary Laser Ranging and Altimetry (PLRA) for industrial and scientific applications. The role of SCF_Lab is fundamental to study and characterize cube corner retroreflectors (CCRs) necessary for laser ranging. CCRs are special “mirrors” that reflect light in the same direction it came from as it was a normal flat mirror but always orthogonal to the beam no matter where the beam actually came from. It happens thanks to a triple rebound of photons, over the three faces of the corner. In SCF_Lab, thanks to an innovative thermal-vacuum-optical test (SCF-Test), we characterize and model the thermal behaviour and the optical performances of CCRs. The laboratory procedures are approved by the international organization that coordinates all laser ranging activities, the International Laser Ranging Service (ILRS). Our key experimental innovation is the concurrent measurement and modelling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of the SLR/LLR payload of retroreflectors under thermal conditions produced with a solar simulator. The primary target is to provide critical design and diagnostic capabilities for SLR to Galileo and other GNSS (Global Navigation Satellite System) constellations. New retroreflectors designs will be fundamental to improve GNSS orbits, increasing, this manner, accuracy, stability, and distribution of the International Terrestrial Reference Frame (ITRF), in order to provide a more precise definition of the geocenter (origin) and the scale (length unit). The SCF_Lab is also developing, validating and optimizing a next-generation LLR arrays for precision tests of GR with the MoonLIGHT-2 (Moon Laser Instrumentation for General relativity High-accuracy Tests - Phase 2) experiment.

The SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and Cube/microsat Characterization Facilities Laboratory) is a specialized infrastructure, unique worldwide, dedicated to design, characterization and modeling of the space segment of Satellite Laser Ranging (SLR), Lunar Laser Ranging (LLR) and Planetary Laser Ranging and Altimetry (PLRA) for industrial and scientific applications. We developed advanced laser retroreflectors for solar system exploration, geodesy and for precision tests of General Relativity (GR) and new gravitational physics. Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of the SLR/LLR payload of retroreflectors under thermal conditions produced with a close-match solar simulator. The primary goal of these innovative tools is to provide critical design and diagnostic capabilities for SLR to Galileo and other GNSS (Global Navigation Satellite System) constellations. The implementation of new retroreflectors designs being studied will be helpful to improve GNSS orbits, increasing, this way, accuracy, stability, and distribution of the International Terrestrial Reference Frame (ITRF), in order to provide a better definition of the geocenter (origin) and the scale (length unit). The SCF is also actively used to develop, validate and optimize 2nd generation LLR arrays for precision tests of GR with the MoonLIGHT-2 (Moon Laser Instrumentation for General relativity High-accuracy Tests — Phase 2) project. Laser ranging and laser reflectors throughout the solar system are also used to develop new fundamental gravity physics models and study the experimental constraints to these models.

Over the past 40 years, Lunar Laser Ranging (LLR, developed by the Univ. of Maryland (PI) and INFN-LNF (Co-PI)) to the Apollo Cube Corner Retroreflector (CCR) arrays have supplied almost all the significant tests of General Relativity (Currie et al., 2009 [12]). LLR can evaluate the PPN (Post Newtonian Parameters), addressing this way both the possible changes in the gravitational constant and the self-energy properties of the gravitational field. In addition, the LLR has provided significant information on the composition and origin of the Moon. This is the only Apollo experiment that is still in operation. Initially the Apollo LLR arrays contributed a negligible fraction of the ranging error budget. Over the decades, the ranging capabilities of the ground stations have improved by more than two orders of magnitude. Now, because of the lunar librations, the existing Apollo retroreflector arrays contribute a significant fraction of the limiting errors in the range measurements. We built a new experimental apparatus (the ‘Satellite/Lunar Laser Ranging Characterization Facility’, SCF) and created a new test procedure (the SCF-Test) to characterize and model the detailed thermal behavior and the optical performance of cube corner laser retroreflectors in space for industrial and scientific applications (Dell’Agnello et al., 2011 [13]). Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of the SLR retroreflector payload under thermal conditions produced with a close-match solar simulator. The apparatus includes infrared cameras for non-invasive thermometry, thermal control and real-time movement of the payload to experimentally simulate satellite orientation on orbit with respect to both solar illumination and laser interrogation beams. These unique capabilities provide experimental validation of the space segment for SLR and Lunar Laser Ranging (LLR). The primary goal of these innovative tools is to provide critical design and diagnostic capabilities for Satellite Laser Ranging (SLR) to Galileo and other GNSS (Global Navigation Satellite System) constellations. Implementation of new retroreflector designs being studied will help to improve GNSS orbits, which will then increase the accuracy, stability, and distribution of the International Terrestrial Reference Frame (ITRF) [4], to provide better definition of the geocenter (origin) and the scale (length unit). The SCF is also actively used to develop, validate and optimize the second generation LLR arrays for precision gravity and lunar science measurements to be performed with robotic missions of the International Lunar Network in which NASA and ASI participate (ILN). The capability will allow us to optimize the design of GNSS laser retroreflector payloads to maximize ranging efficiency, to improve signal-to-noise conditions in daylight and to provide pre-launch validation of retroreflector performance under laboratory-simulated space conditions. For the MAGIA lunar orbiter Phase A study funded by ASI (Dell’Agnello et al., 2010 [14]), we studied fundamental physics and absolute positioning metrology experiments, to improve test of the gravitational redshift in the Earth–Moon system predicted by General Relativity and a precursor test of our second generation LLR payload.

Since the 1970s Lunar Laser Ranging (LLR) to the Apollo Cube Corner Retroreflector (CCR) arrays (developed by the University of Maryland, UMD) have supplied significant tests of General Relativity: possible changes in the gravitational constant, gravitational self-energy, weak equivalence principle, geodetic precession, inverse-square force-law. LLR has also provided significant information on the composition and origin of the Moon. This is the only Apollo experiment still in operation. In the 1970s Apollo LLR arrays contributed a negligible fraction of the ranging error budget. Since the ranging capabilities of ground stations improved by more than two orders of magnitude, now, because of the lunar librations, Apollo CCR arrays dominate the error budget. With the project MoonLIGHT (Moon Laser Instrumentation for General relativity High-accuracy Tests), in 2006 INFN-LNF joined UMD in the development and test of a new-generation LLR payload made by a single, large CCR (100 mm diameter) unaffected by librations. In particular, INFN-LNF built and is operating a new experimental apparatus (Satellite/lunar laser ranging Characterization Facility, SCF) and created a new industry-standard test procedure (SCF-Test) to characterize and model the detailed thermal behavior and the optical performance of CCRs in laboratory-simulated space conditions, for industrial and scientific applications. Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of retroreflector payloads under thermal conditions produced with a solar simulator. The apparatus includes infrared cameras for non-invasive thermometry, thermal control and real-time payload movement to simulate satellite orientation on orbit with respect to solar illumination and laser interrogation beams. These capabilities provide: unique pre-launch performance validation of the space segment of LLR/SLR (Satellite Laser Ranging); retroreflector design optimization to maximize ranging efficiency and signal-to-noise conditions in daylight. Results of the SCF-Test of our CCR payload will be presented. Negotiations are underway to propose our payload and SCF-Test services for precision gravity and lunar science measurements with next robotic lunar landing missions. We will describe the addition of the CCR optical Wavefront Fizeau Interferogram (WFI) concurrently to FFDP/temperature measurements in the framework of an ASI-INFN project, ETRUSCO-2. The main goals of the latter are: development of a standard GNSS (Global Navigation Satellite System) laser Retroreflector Array; a second SCF; SCF-Test of Galileo, GPS and other ‘as-built’ GNSS retroreflector payloads. Results on analysis of Apollo LLR data and search of new gravitational physics with LLR, Mercury Radar Ranging will be presented.

We built a new experimental apparatus (the “Satellite/lunar laser ranging Characterization Facility”, SCF) and created a new test procedure (the SCF-Test) to characterize and model the detailed thermal behavior and the optical performance of cube corner laser retroreflectors in space for industrial and scientific applications. The primary goal of these innovative tools is to provide critical design and diagnostic capabilities for Satellites Laser Ranging (SLR) to Galileo and other GNSS (Global he capability will allow us to optimize the design of GNSS laser retroreflector payloads to maximize ranging efficiency, to improve signal-to-noise conditions in daylight and to provide pre-launch validation of retroreflector performance under laboratory-simulated space conditions. Implementation of new retroreflector designs being studied will help to improve GNSS orbits, which will then increase the accuracy, stability, and distribution of the International Terrestrial Reference Frame (ITRF), to provide better definition of the geocenter (origin) and the scale (length unit). Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of the SLR retroreflector payload under thermal conditions produced with a close-match solar simulator. The apparatus includes infrared cameras for non-invasive thermometry, thermal control and real-time movement of the payload to experimentally simulate satellite orientation on orbit with respect to both solar illumination and laser interrogation beams. These unique capabilities provide experimental validation of the space segment for SLR and Lunar Laser Ranging (LLR). We used the SCF facility and the SCF-Test to perform a comprehensive, non-invasive space characterization of older generation, back-coated retroreflectors of the GIOVE-A and -B (Galileo In-Orbit Validation Elements) and the GPS-35 and -36 designs. First, using a full GPS flight model at laser wavelengths of 532 and 632 nm, we found its “effective optical cross section” in air, under isothermal conditions, to be six times lower than the Retroreflector Standard for GNSS satellites (100 106 m2 at 20,000 km altitude for GPS and 180 106 m2 for Galileo at 23,200 km altitude), issued by the International Laser Ranging Service (ILRS). Under the simulated thermal and space conditions of the SCF, we also showed that in some space configurations the “effective optical cross section” is further reduced, by the thermal degradation of the FFDP. Using the same SCF-Test configuration on an individual GIOVE prototype cube, we measured severe thermal degradation in optical performance, which appears to be caused by the retroreflector metal coating and the nonoptimized thermal conductance of the mounting. Uncoated retroreflectors with proper mounting can minimize thermal degradation and significantly increase the optical performance, and as such, are emerging as the recommended design for modern GNSS satellites. The COMPASS-M1, GLONASS-115 GNSS satellites use uncoated cubes. They provide better efficiency than those on GPS and GIOVE, including better daylight ranging performance. However, these retroreflectors were not characterized in the laboratory under space conditions prior to launch, so we have no basis to evaluate how well they were optimized for future GNSS satellites. SCF-Testing, under a non-disclosure agreement between INFN-LNF and the European Space Agency (ESA), of prototype uncoated cubes for the first four Galileo satellites to be launched (named “IOV”, In-Orbit Validation satellites) is a major step forward. An SCF-Test performed on a LAGEOS (LAser GEOdynamics Satellite) engineering model retroreflector array provided by NASA, showed the good space performance on what is now a reference ILRS payload standard. The IOV and LAGEOS measurements demonstrated the effectiveness of the SCF-Test as an LRA diagnostic, optimization and validatio...

Thorough laboratory measurements performed at INFN-LNF (Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Frascati), in the framework of the ETRUSCO (Extra Terrestrial Ranging to Unified Constellations) experiment, proved fundamental to characterize retroreflectors for GNSS (Global Navigation Satellite System) satellites. The standard test developed, SCF-Test, was important to outline the weaknesses of past retroreflectors payloads (in use on GPS, GLONASS and GIOVE A/B satellites). For the upcoming deployment of the Galileo constellation ESA requested, in 2010, a full SCF-Test campaign to characterize a prototype retroreflector of the first IOV satellites. We report the results of a standard SCF-Test and the test of a simulated orbit, called GCO (Galileo Critical half-Orbit). The experience gathered with the ETRUSCO experiment was important for the subsequent project, ETRUSCO-2, whose aim is to develop and measure, in a newly built facility, a full size array of retroreflectors to be deployed on GNSS constellations. Here we report preliminary concurrent thermal and optical simulations of a simulated array. A simplified structure of the array was subject to a simulated space environment in a GCO; the resulting temperature distribution inside each retroreflector, was the input of the optical software to determine the variation of the intensity, throughout the orbit, coming back at a ranging station. The goal is to limit as much as possible signal fluctuations with respect to current deployed arrays.

Over the past forty years, Lunar Laser Ranging (LLR) to the Apollo Corner Cube Reflector (CCR) arrays has supplied almost all of the significant tests of General Relativity, and provided significant information on the composition and origin of the Moon. These arrays are the only experiment of the Apollo program still in operation. Initially the Apollo Lunar arrays contributed a negligible portion of the error budget used to achieve these results. However over the decades, the performance of the ground stations has been greatly upgraded so that the ranging accuracy has improved by more than two orders of magnitude. Now, after forty years, because of the lunar librations, the existing Apollo retroreflector arrays contribute a significant fraction of the limiting errors in the range measurements. University of Maryland (UMD) and INFN/LNF are now proposing a new approach to the Lunar Laser Ranging Array technology, the experiment MoonLIGHT12. The new arrays will support ranging observations that are a factor 100 more accurate, reaching the micron level. The new fundamental physics and lunar physics that this new Lunar Laser Ranging Retroreflector Array for the 21st century (LLRRA-21) can provide, will be briefly described. The new lunar CCR housing has been built at the INFN/LNF3. In the design of the new array there are three major challenges: 1) validate that the specifications of the CCR required for the new array, which are significantly beyond the properties of current CCRs, can indeed be achieved, 2) address the thermal and optical effects of the absorption of solar radiation within the CCR, reduce the transfer of heat from the hot housing to the CCR and 3) define a method of emplacing the CCR package on the lunar surface such that the relation between the optical center of the array and the center of mass of the Moon remains stable over the lunar day/night cycle. Its evolutionary design may be suitable for future GNSS constellations guaranteeing ranging accuracy improvement (the concept of a single reflector introduces no laser pulse spreading at all angles), weight and area saving (being its absolute optical cross section equal to a large number of the CCRs that will be used for the upcoming GNSS constellations)4.

We describe the INFN-LNF standard procedure for the optical Far Field Diffraction Pattern (FFDP) test of cube corner laser retroreflectors (CCRs) for space applications, when these CCRs are in air and in isothermal conditions around (22 ± 2)°C. This procedure was developed in 2007 and 2008, using prototype GLONASS CCRs lent to LNF by IPIE of Moscow and a GPS-2 flight model CCR array lent to LNF by the University of Maryland at College Park (all using Al-coated fused silica retroreflectors of 27 mm diameter). This was done in the context of the INFN experiment ETRUSCO2. The modeling of FFDP measurements is performed with a commercial software, CodeV by O.R.A. Inc., and it has been cross-checked against two independent software programs developed by other two members of the ILRS �??Signal Processing Working Group�?�, D. Arnold and T. Otsubo, finding very good agreement among the three. In summer 2008 this procedure has been validated by performing the FFDP test of the LAGEOS �??Sector�?�, an engineering prototype on loan from NASA-GSFC, equipped with 37 uncoated, fused silica retroreflectors of 38 mm diameter. We report test results for the GLONASS and LAGEOS CCRs. Details of the test procedure and CodeV simulations are given for the particular case of the LAGEOS Sector.

The "Satellite/lunar laser ranging Characterization Facility" (SCF) of INFN-LNF in Frascati, Italy, is devoted to the characterization of the detailed thermal properties and the optical performance of laser- ranged payloads (the "SCF-test") for GNSS, Space Geodesy and Fundamental Physics applications [1][2]. The Optical Lab is a second LNF facility dedicated to the far field diffraction pattern (FFDP) industrial acceptance test of laser cube corner retroreflectors (CCR) for space applications. We tested about 200 flight CCRs to be deployed in space by imminent launches at the two LNF facilities. These launches are for the current American Global Navigation Satellite System Constellation, the GPS-2 by NASA and for the European VEGA Program, by ESA/ASI. Some of the tested CCRs are for undisclosed missions by other space agencies. Deep Space Gravity Probe (DSGP) is a mission led by NASA-JPL (S. Turyshev is the PI), proposed to NASA and to the ESA "Cosmic Vision" program to study the anomalous deceleration of the Pioneer 10 and 11 probes and other important interplanetary science topics. In the context of a three-year study on "Cosmology and Fundamental Physics" (COFIS) funded by ASI and led at national level by P. de Bernardis we designed a prototype laser-ranged test mass for the DSGP satellite formation. This mass is being built at LNF and will be SCF-Tested at the SCF. We are also collaborating with NASA-GSFC (J. McGarry et al) on the test of innovative CCRs for the GPS-3. The goal of this R&D is to convince the US Air Force and Department of Defense of the full functionality of the hollow retroreflector design. This is a prerequisite to propose the deployment of retroreflectors on the GPS-3, which, unlike GALILEO, is a military constellation.

Il Consigio di Amministrazione dell'ASI, nella sua seduta del 7/2/2008, ha individuato le cinque proposte, nell'ambito del Bando Piccole Missioni, di cui verrà finanziato lo studio di Fase A, ovvero lo studio di fattibilità preliminare alla scelta delle due missioni che verranno lanciate entro il 2014. Una di queste cinque missioni è MAGIA (Missione Altimetrica Gravimetrica geochimica Italiana lunAre), di cui il Principal Investigator è la Prof. A. Coradini (INAF-IFSI) e il Prime Industriale è Rheinmetall Italia S.p.A. La missione si propone di rispondere ad alcune delle questioni di maggiore importanza per lo studio della Luna quali la struttura interna, elemento necessario per comprendere l'origine e la formazione, la ricerca di evidenze di processi di differenziazione che devono aver caratterizzato la parte iniziale della formazione e la correlazione con la successiva fase dominata dalla craterizzazione della superficie. Al momento, i dati geochimici e mineralogici da telerilevamento lunare, utili per raccordare le analisi dei campioni di rocce prelevate in-situ ad aree del satellite più vaste, sono disponibili solo per la "near side". Inoltre anche le missioni più recenti (Clementine, SMART-1, Lunar Prospector) non avevano a bordo strumenti in grado di effettuare un'analisi mineralogica accurata. MAGIA si propone inoltre una precisa caratterizzazione del campo gravitazionale lunare, ed ad un'accurata misura del suo stato rotazionale. Questi temi sono tutti strettamente legati tra loro concorrendo, infatti, a migliorare la comprensione dell'origine ed evoluzione della Luna. Inoltre, MAGIA mostrerà come si possa utilizzare una piattaforma in orbita circumlunare al fine di ottenere misure di fisica fondamentale, quali un miglioramento delle misura del redshift gravitazionale, una "precursor mission" per la proposta di Lunar Laser Ranging di seconda generazione, MoonLIGHT, ed un potenziale ulteriore miglioramento dei test delle Relatività Generale grazie ad una misura indipendente della posizione del selenocentro rispetto a Terra. Questo Report descrive il pacchetto di Fisica Fondamentale della proposta MAGIA.

We describe the basic goals of the ETRUSCO experiment and the work done in 2006, together with our international collaborators, which led to the approval of the proposal by the INFN-CSNV in October 2006.Some of the 2007 funds were made available in November 2006 and were used to buy optical instrumentation. In 2007 the LNF Satellite laser ranging Characterization Facility (SCF) has been upgraded to perform integrated laser ranging tests and thermal measurements (SCF-Test) of the planar retro-reflector arrays installed on the satellites of GNSS constellations. This will be done in a realistic environment, which simulates the orbital conditions of the GPS-2 (USA), GLONASS (Russia), and soon GALILEO (EU), at altitudes of about 20000-23000 Km. The year 2007 has been devoted to the SCF-Test of a prototype model of a retro-reflector deployed on the two of GPS-2 satellites, on the GLONASS constellation and on GIOVE-A and GIOVE-B, the prototypes of GALILEO. This SCF-Test has been successful and data analysis is well underway. The experimental work at the SCF will also be compared to software models of the thermal, structural, orbital and optical behavior of the prototypes. Detailed thermal models of the LAGEOS-type retro-reflectors have already been built and checked with SCF measurements. Work is in progress to develop these models also for the GNSS.The year 2008 is dedicated to the SCF-Test of a flight model of a retro-reflector array to be deployed on one of the next GPS-2 satellites.The long-term goal of ETRUSCO is to perform at LNF the SCF-Test the larger and more important GALILEO laser retro-reflector arrays. Planning and provisions to reach this goal are well underway: in fact, INFN-LNF is participating to a call for tender for the 'Support to the Coordination of the European GALILEO Simulation and Testing Infrastructure', issued by the Galileo Supervisory Authority, in the context of FP7-GALILEO. The result of the tender is due by October 2008.

New robotic lunar landings may take place during next decade. The Italian Space Agency (ASI) has requested proposals for interesting and compelling physics experiments to be performed with the severe weight, size, power and deployment restrictions inherent to lunar sorties. MoonLIGHT-R is a proposal for improving by a factor 1000 or more the accuracy of the current Lunar Laser Ranging (LLR) experiment, performed since 1969 with retro-reflector arrays deployed by Apollo 11, 14 and 15. LLR is the only Apollo experiment still taking data today. Achieving this goal requires a new, different thermal, optical and mechanical design of the retro-reflector array and detailed simulations and experimental tests. MoonLIGHT-R is a light, compact, very-long lasting, maintenance-free and completely passive payload. MoonLIGHT-R will perform accurate tests of General Relativity (GR) already with the existing ILRS systems (like ASI-MLRO) . This accuracy will get better and better as laser technologies improve over the next few decades, like they did relentlessly since the invention of the laser in the '60s. A specific cosmological model, which explains the acceleration of the Universe via modified GR at very large distances, can be fully tested by measuring an anomalous precession of the Moon perigee. A high scientific return is guaranteed. We are committed to the space-climatic and laser-optical simulation (and, at a later stage, experimental characterization) of the new LLR array using the LNF Space Climatic Facility (SCF). The payload construction and deployment is an opportunity for the national industries. Preliminary space-climatic simulations and payload specs are presented in this LNF report.

New manned lunar landings may take place during next decade. In view of this possibility, space agencies around the word have requested to the international scientific community proposals for interesting and compelling physics experiments to be performed with the severe weight, size, power and deployment restrictions inherent to the first lunar sorties. Answering the recent NASA call "Suitcase Science to the Moon", a group formed by INFN-LNF, Astronaut Roberto Vittori of the Italian Air Force and several US research institutions has presented a proposal for improving by a factor 1000 or more the accuracy of the current Lunar Laser Ranging (LLR) experiment (performed in the last 37 years using the retro-reflector arrays deployed on the Moon by the Apollo 11, 14 and 15 missions). Achieving such an improvement requires a modified thermal, optical and mechanical design of the retro-reflector array and detailed experimental tests. The new experiment will allow a rich program of accurate tests of General Relativity already with current laser ranging systems. This accuracy will get better and better as the performance of laser technologies improve over the next few decades, like they did relentlessly since the '60s. The LNF group has committed itself to perform the full climatic simulation and experimental characterization of the new retro-reflector prototypes using the new INFN-LNF "Space Climatic Facility"(SCF). Preliminary simulations are reported in this document. The space-climatic, laser-optical studies and tests will be done by members of this ITALY-US collaboration, because they are deeply linked to the proposed physics measurements. For the mechanics support structures and the "suitcase" there is window of work opportunity for industries. This internal LNF report (pages 2-21) is an excerpt from the Proposal presented to NASA on October 27 2006 by the authors listed at page 2. MoonLIGHT-M is the internal LNF name given to this Proposal (where "-M" indicates that this is intended for a Manned mission)

The LAGEOS I and II satellites have been launched, respectively, in 1976 (by NASA) and 1992 (NASA-ASI) into orbits with high inclinations (i = 109.9° and 52.65°), low eccentricities (e = 0.004 and 0.014) and large semi-major axes (a = 12,270 and 12,163 km). They are high-accuracy, completely passive, spherical test masses, whose orbit is tracked with