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Papers by Oberto Citterio

Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II

The conventional state-of-the-art manufacturing processes of aspheric reflective optics normally ... more The conventional state-of-the-art manufacturing processes of aspheric reflective optics normally consists of the following steps: • Production of the glass blank; • Machining and grinding of the blank to approximate shape, inclusive of backside lightening; • Deterministic figuring and polishing. Deterministic figuring and polishing are iterative processes performed by IRP (Intelligent Robot Polishing) or MRF (Magneto-Rheological Figuring) or IBF (Ion-Beam Figuring), which iteratively converge to the targeted performance with guidance from accurate metrology information. The process capability of these one-off methods is well established, but hardly cost-effective for any small/large series production because of the need to repeat the entire process for each product unit. Differently from the conventional methods, the Cold Shaping Optics manufacturing technology consists of precisely shaping an inexpensive thin glass sheet (⪆ 1 mm) over a high precision mandrel and freezing its shape over a low-cost substrate by means of an epoxy adhesive layer. The mandrel must have the same surface shape accuracy specified for the desired optics. However, in a mini production series, the Cold Shaping Optics technique can reduce the recurrent production costs by amortizing the cost of the re-usable shaping mandrel over multiple product units allowing the manufacture of high-performance reflective optics at a fraction of the cost of traditional grinding and polishing methods. In addition to that, the possibility of actively changing the shape of the mandrel allows the series production of optics with different shapes from the same mandrel, hence further reducing the cost paradigm. In this paper we report the results obtained during the development of first prototype mirrors of 380 mm diameter.

Simbol-X is arguably the most powerful broad-band focusing hard (0.5-80 keV) X-ray telescope oper... more Simbol-X is arguably the most powerful broad-band focusing hard (0.5-80 keV) X-ray telescope operating in the 2013 timeframe. The combination of good angular resolution, broad energy response, and efficient observing provided by a good field of view and high orbit will provide a very large increase in sensitivity in a hitherto relatively unexplored spectral region. This will enable key scientific

The Wide Field X-ray Telescope is the latest in a series of mission concepts to carry out a large... more The Wide Field X-ray Telescope is the latest in a series of mission concepts to carry out a large area X-ray survey with sensitivity orders of magnitude fainter than the ROSAT All Sky Survey, and with angular resolution of 5 arcsec over the entire survey area. The science that can be addressed by such a mission and the technical readiness are discussed. The conclusion is that WFXT addresses many of the science issues raised in the 2010 New World New Horizons decadal survey and is well matched to the next generation of optical, IR and radio surveys currently being planned. The technologies needed for WFXT have all been demonstrated, and only the mirrors have a technical readiness level (TRL) that is less than 6. Three independent cost estimates for this mission, covering lifecycle costs, launch services and a GO program are below $1B (FY12), and suggest that the mission concept is mature and ready for implementation.

A new technology is under development to grow layers of amorphous Silicon Carbide in vacuum at te... more A new technology is under development to grow layers of amorphous Silicon Carbide in vacuum at temperatures below 200°C by PE-CVD technology. The layers can be used either to improve the surface quality of mirror substrates, as a polishable cladding coating, or to form self-sustaining thin mirrors in SiC. The former application is useful in particular for the coating of

Xeus Studying the Evolution of the Hot Universe, 2003

One of the major components of the XEUS scientific payload is given by the X-ray optics that, in ... more One of the major components of the XEUS scientific payload is given by the X-ray optics that, in spite of its enormous size, has even to be characterized by optimal imaging capabilities (the HEW goal is of just 2 arcsec). The enormous mirror dimensions give rise to a number of problems that make very challenging to meet a so ambitious

SPIE Proceedings, 1989

In the last years the interest in high throughput focusing x-ray optics has been increasing rathe... more In the last years the interest in high throughput focusing x-ray optics has been increasing rather rapidly. High photon collecting power is the most important requirement in scientific investigations that require for example measurement of line emission and temporal behavior of sources. Generally this type of observations need 10 time or more photons than source detection and position. Because of the operation at grazing incidence an high throughput x-ray telescope requires to be composed of a large number of nested confocal mirrors. To reduce the losses imposed by the obstruction of the mirrors wall and to keep the weight of the optical system within acceptables values, the thickness of the mirrors must be very thin. Nevertheless the angular resolution of the optics must be of a good standard (better than 1 min. of arc) in order to avoid sources confusion. The techniques of replicating the mirror shells from masters are capable to produce x-ray optics in accordance with the above mentioned requirements. The method of epoxy replication will be briefly reviewed in the paper while the technique of replica by electroforming will be discussed in more details, underlining the possibility of using more elaborated electroforming processes for the manufacture of light weight large aperture x-ray optics.

We are studying a Large Area X-ray Spectroscopy Mission conceived and sized to address a range of... more We are studying a Large Area X-ray Spectroscopy Mission conceived and sized to address a range of fundamental astrophysical questions such as: - the role of flares and microflares in heating stellar coronae - the impact of metallicity on the Eddington limit in accreting binaries - the enrichment of the interstellar and intracluster medium - the formation of galaxies from

Memorie Della Societa Astronomica Italiana, Mar 1, 1978

ABSTRACT

Proceedings of Spie the International Society For Optical Engineering, 1997

Nowadays the most used technology to obtain thin and light mirror shells for x-ray optics is the ... more Nowadays the most used technology to obtain thin and light mirror shells for x-ray optics is the replica technique by nickel electroforming. This technology has been successfully employed for projects like SAX, JET-X and XMM. Nevertheless, the high density of the nickel poses some limitations to the possibility of extending the use of this technology for the future x-ray missions demanding high collecting area, good angular resolution and low weight of the optics. In the paper we analyze which are the present limits of the nickel electroforming technology and we underline the potentiality of using SiC and other ceramic materials for the manufacture of large and light x-ray optics. Possible manufacturing process are proposed and preliminary results of prototypes of ceramic mirror shells are presented.

The Constellation-X mission planned for launch in 2015, will feature an array of Hard X-ray teles... more The Constellation-X mission planned for launch in 2015, will feature an array of Hard X-ray telescopes (HXT) whose bandwidth extends to \ 70 keV. Several technologies are being investigated for fabrication of these optics, including multilayer Coated Electroformed-Nickel-Replicated (ENR) shells. We are building a prototype HXT mirror module using an ENR process to fabricate the in dividual shells.This prototype consists of 5 shells with diameters ranging from 150 mm to 280 mm with a length of 426 mm. This paper presents a progress update and focuses on accomplishments during this past year. In particular, we will present results from high energy full illumination tests, taken at the MPE Panter Test Facility. This work was supported in part by NASA Grant NNG05WC27G and CONX/NASA grant 44A-1046805.

Multilayer and Grazing Incidence X Ray Euv Optics For Astronomy and Projection Lithography, 1993

The following procedure is used to evaluate modifications of the optical performances of the JET-... more The following procedure is used to evaluate modifications of the optical performances of the JET-X telescope mirror shells (MS) due to manufacturing, integration tolerancing, gravity, and thermal gradients: analysis of the deformed shape of the MS by means of the ADINA finite element (FE) code, and optical performance analysis by means of a ray tracing code (RTC) for the Wolter 1 telescope directly interfaced with the FE code output. For the different conditions analyzed, half power radius, encircled energy, and spot diagrams are computed. Numerical analyses are performed for the single mirror shells and for the whole mirror module. The numerical models used are described, and the main features of the RTC and the relevant results are discussed.

Proceedings of Spie the International Society For Optical Engineering, Aug 1, 2005

The Constellation-X (Con-X) mission planned for launch in 2015, will feature an array of Hard X-r... more The Constellation-X (Con-X) mission planned for launch in 2015, will feature an array of Hard X-ray telescopes (HXT) with a total collecting area greater than 1500 cm2 at 40 keV. Two technologies are being investigated for the optics of these telescopes, including multilayer coated Electroformed-Nickel-Replicated (ENR) shells. The attraction of the ENR process is that the resulting full-shell optics are inherently stable and offer the prospect of better angular resolution which results in lower background and higher instrument sensitivity. We are building a prototype HXT mirror module using an ENR process to fabricate the individual shells. This prototype consists of 5 shells with diameters ranging from 150 mm to 280 mm with a length of 426 mm. The innermost of these will be coated with iridium, while the remainder will be coated with graded d-spaced W/Si multilayers. Parts I and II of this work were presented at the SPIE meetings in 2003 and 2004. This paper presents a progress update and focuses on accomplishments during this past year. In particular, we will present results from full illumination X-ray tests of multilayer coated shells, taken at the MPE-Panter X-ray facility.

Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II

The conventional state-of-the-art manufacturing processes of aspheric reflective optics normally ... more The conventional state-of-the-art manufacturing processes of aspheric reflective optics normally consists of the following steps: • Production of the glass blank; • Machining and grinding of the blank to approximate shape, inclusive of backside lightening; • Deterministic figuring and polishing. Deterministic figuring and polishing are iterative processes performed by IRP (Intelligent Robot Polishing) or MRF (Magneto-Rheological Figuring) or IBF (Ion-Beam Figuring), which iteratively converge to the targeted performance with guidance from accurate metrology information. The process capability of these one-off methods is well established, but hardly cost-effective for any small/large series production because of the need to repeat the entire process for each product unit. Differently from the conventional methods, the Cold Shaping Optics manufacturing technology consists of precisely shaping an inexpensive thin glass sheet (⪆ 1 mm) over a high precision mandrel and freezing its shape over a low-cost substrate by means of an epoxy adhesive layer. The mandrel must have the same surface shape accuracy specified for the desired optics. However, in a mini production series, the Cold Shaping Optics technique can reduce the recurrent production costs by amortizing the cost of the re-usable shaping mandrel over multiple product units allowing the manufacture of high-performance reflective optics at a fraction of the cost of traditional grinding and polishing methods. In addition to that, the possibility of actively changing the shape of the mandrel allows the series production of optics with different shapes from the same mandrel, hence further reducing the cost paradigm. In this paper we report the results obtained during the development of first prototype mirrors of 380 mm diameter.

Simbol-X is arguably the most powerful broad-band focusing hard (0.5-80 keV) X-ray telescope oper... more Simbol-X is arguably the most powerful broad-band focusing hard (0.5-80 keV) X-ray telescope operating in the 2013 timeframe. The combination of good angular resolution, broad energy response, and efficient observing provided by a good field of view and high orbit will provide a very large increase in sensitivity in a hitherto relatively unexplored spectral region. This will enable key scientific

The Wide Field X-ray Telescope is the latest in a series of mission concepts to carry out a large... more The Wide Field X-ray Telescope is the latest in a series of mission concepts to carry out a large area X-ray survey with sensitivity orders of magnitude fainter than the ROSAT All Sky Survey, and with angular resolution of 5 arcsec over the entire survey area. The science that can be addressed by such a mission and the technical readiness are discussed. The conclusion is that WFXT addresses many of the science issues raised in the 2010 New World New Horizons decadal survey and is well matched to the next generation of optical, IR and radio surveys currently being planned. The technologies needed for WFXT have all been demonstrated, and only the mirrors have a technical readiness level (TRL) that is less than 6. Three independent cost estimates for this mission, covering lifecycle costs, launch services and a GO program are below $1B (FY12), and suggest that the mission concept is mature and ready for implementation.

A new technology is under development to grow layers of amorphous Silicon Carbide in vacuum at te... more A new technology is under development to grow layers of amorphous Silicon Carbide in vacuum at temperatures below 200°C by PE-CVD technology. The layers can be used either to improve the surface quality of mirror substrates, as a polishable cladding coating, or to form self-sustaining thin mirrors in SiC. The former application is useful in particular for the coating of

Xeus Studying the Evolution of the Hot Universe, 2003

One of the major components of the XEUS scientific payload is given by the X-ray optics that, in ... more One of the major components of the XEUS scientific payload is given by the X-ray optics that, in spite of its enormous size, has even to be characterized by optimal imaging capabilities (the HEW goal is of just 2 arcsec). The enormous mirror dimensions give rise to a number of problems that make very challenging to meet a so ambitious

SPIE Proceedings, 1989

In the last years the interest in high throughput focusing x-ray optics has been increasing rathe... more In the last years the interest in high throughput focusing x-ray optics has been increasing rather rapidly. High photon collecting power is the most important requirement in scientific investigations that require for example measurement of line emission and temporal behavior of sources. Generally this type of observations need 10 time or more photons than source detection and position. Because of the operation at grazing incidence an high throughput x-ray telescope requires to be composed of a large number of nested confocal mirrors. To reduce the losses imposed by the obstruction of the mirrors wall and to keep the weight of the optical system within acceptables values, the thickness of the mirrors must be very thin. Nevertheless the angular resolution of the optics must be of a good standard (better than 1 min. of arc) in order to avoid sources confusion. The techniques of replicating the mirror shells from masters are capable to produce x-ray optics in accordance with the above mentioned requirements. The method of epoxy replication will be briefly reviewed in the paper while the technique of replica by electroforming will be discussed in more details, underlining the possibility of using more elaborated electroforming processes for the manufacture of light weight large aperture x-ray optics.

We are studying a Large Area X-ray Spectroscopy Mission conceived and sized to address a range of... more We are studying a Large Area X-ray Spectroscopy Mission conceived and sized to address a range of fundamental astrophysical questions such as: - the role of flares and microflares in heating stellar coronae - the impact of metallicity on the Eddington limit in accreting binaries - the enrichment of the interstellar and intracluster medium - the formation of galaxies from

Memorie Della Societa Astronomica Italiana, Mar 1, 1978

ABSTRACT

Proceedings of Spie the International Society For Optical Engineering, 1997

Nowadays the most used technology to obtain thin and light mirror shells for x-ray optics is the ... more Nowadays the most used technology to obtain thin and light mirror shells for x-ray optics is the replica technique by nickel electroforming. This technology has been successfully employed for projects like SAX, JET-X and XMM. Nevertheless, the high density of the nickel poses some limitations to the possibility of extending the use of this technology for the future x-ray missions demanding high collecting area, good angular resolution and low weight of the optics. In the paper we analyze which are the present limits of the nickel electroforming technology and we underline the potentiality of using SiC and other ceramic materials for the manufacture of large and light x-ray optics. Possible manufacturing process are proposed and preliminary results of prototypes of ceramic mirror shells are presented.

The Constellation-X mission planned for launch in 2015, will feature an array of Hard X-ray teles... more The Constellation-X mission planned for launch in 2015, will feature an array of Hard X-ray telescopes (HXT) whose bandwidth extends to \ 70 keV. Several technologies are being investigated for fabrication of these optics, including multilayer Coated Electroformed-Nickel-Replicated (ENR) shells. We are building a prototype HXT mirror module using an ENR process to fabricate the in dividual shells.This prototype consists of 5 shells with diameters ranging from 150 mm to 280 mm with a length of 426 mm. This paper presents a progress update and focuses on accomplishments during this past year. In particular, we will present results from high energy full illumination tests, taken at the MPE Panter Test Facility. This work was supported in part by NASA Grant NNG05WC27G and CONX/NASA grant 44A-1046805.

Multilayer and Grazing Incidence X Ray Euv Optics For Astronomy and Projection Lithography, 1993

The following procedure is used to evaluate modifications of the optical performances of the JET-... more The following procedure is used to evaluate modifications of the optical performances of the JET-X telescope mirror shells (MS) due to manufacturing, integration tolerancing, gravity, and thermal gradients: analysis of the deformed shape of the MS by means of the ADINA finite element (FE) code, and optical performance analysis by means of a ray tracing code (RTC) for the Wolter 1 telescope directly interfaced with the FE code output. For the different conditions analyzed, half power radius, encircled energy, and spot diagrams are computed. Numerical analyses are performed for the single mirror shells and for the whole mirror module. The numerical models used are described, and the main features of the RTC and the relevant results are discussed.

Proceedings of Spie the International Society For Optical Engineering, Aug 1, 2005

The Constellation-X (Con-X) mission planned for launch in 2015, will feature an array of Hard X-r... more The Constellation-X (Con-X) mission planned for launch in 2015, will feature an array of Hard X-ray telescopes (HXT) with a total collecting area greater than 1500 cm2 at 40 keV. Two technologies are being investigated for the optics of these telescopes, including multilayer coated Electroformed-Nickel-Replicated (ENR) shells. The attraction of the ENR process is that the resulting full-shell optics are inherently stable and offer the prospect of better angular resolution which results in lower background and higher instrument sensitivity. We are building a prototype HXT mirror module using an ENR process to fabricate the individual shells. This prototype consists of 5 shells with diameters ranging from 150 mm to 280 mm with a length of 426 mm. The innermost of these will be coated with iridium, while the remainder will be coated with graded d-spaced W/Si multilayers. Parts I and II of this work were presented at the SPIE meetings in 2003 and 2004. This paper presents a progress update and focuses on accomplishments during this past year. In particular, we will present results from full illumination X-ray tests of multilayer coated shells, taken at the MPE-Panter X-ray facility.