Search

In this paper, we report on X-ray transition-edge sensor (TES) microcalorimeters optimized to have the best possible energy resolution for a limited energy range for the incoming X-rays, such as an energy resolution of 0.3 eV full width half maximum (FWHM) for energies up to $$\approx 0.8\,{\mathrm{keV}}$$ as is desirable for one of the Lynx X-ray Microcalorimeter subarrays. The test array we have fabricated has $$60\times 60$$ sensors on a pitch of $$50\,\upmu {\mathrm{m}}$$, and has $$46\times 46\,\upmu {\mathrm{m}}^2$$ absorbers that are one micrometer thick. We have measured a spectral energy resolution of the same device using 3 eV photons delivered through an optical fiber. For the one-photon 3 eV line, we have obtained an energy resolution of 0.25 eV FWHM, which is consistent with the estimated performance based on the signal size and noise. Further measurements will determine how the energy resolution degrades with energy. Based upon measurements of the TES transition characteristics, it appears that this level of energy resolution should be achievable up to 0.5 keV, and the performance will then gradually degrade to the measured energy resolution of around 2.3 eV at 1.5 keV. In this paper, we describe the full design and characterization of this detector, and discuss the performance limits of pixels designs like this.

We report on the development of multi-absorber transition edge sensors (TESs), referred to as hydras. A hydra consists of multiple x-ray absorbers each with a different thermal conductance to a TES. Position information is encoded in the pulse shape. With some trade-off in performance, hydras enable very large format arrays without the prohibitive increase in bias and read-out components associated with arrays of individual TESs. Hydras are under development for the next generation of space telescope such as Lynx. Lynx is a NASA concept under study that will combine a < 1 arcsecond angular resolution optic with 100,000-pixel microcalorimeter array with energy resolution of deltaE_FWHM ~ 3 eV in the soft x-ray energy range. We present first results from hydras with 25-pixels for Lynx. Designs with absorbers on a 25 micron and 50 micron pitch are studied. Arrays incorporate, for the first time, microstrip buried wiring layers of suitable pitch and density required to readout a full-scale Lynx array. The resolution from the coadded energy histogram including all 25-pixels was deltaE_FWHM = 1.66+/-0.02 eV and 3.34+/-0.06 eV at an energy of 1.5 keV for the 25 micron and 50 micron absorber designs respectively. Position discrimination is demonstrated from parameterization of the rise-time., 7 pages, 5 figures. Low Temperature Detectors 18 Conference, Milan Italy

We describe the performance of position-sensitive metallic magnetic calorimeter X-ray detectors for potential future astrophysics missions, such as Lynx. The motivation behind this is to achieve a large focal plane area by increasing the number of pixels compared to the number of readout channels (called hydra). The detector consists of a $$5 \times 5$$ array of gold absorbers thermally coupled to a paramagnetic sensor. Since each absorber has a different thermal link to the sensor, it generates a different pulse shape and enables discrimination of pixel position. Recently, we have been successfully able to discriminate 25 averaged pulse shapes by means of rise-time and pulse height. The measured pulse shapes and distribution agree well with the modeling results. The estimated energy resolutions based on the pulse height and noise data we measured are 2.8–3.7 eV for $$\hbox {MnK}\alpha $$ X-ray photons at 50 mK.

Future astrophysics missions such as the Lynx X-ray Microcalorimeter will comprise a very large array of X-ray microcalorimeters with greater than 100 000 pixels. One of the major challenges associated with the realization of large format arrays is the fabrication of high-density, high-yield, superconducting wiring between the pixels of the array. An attractive way to overcome this challenge is to use buried layers of multilayer wiring. Here we report on the fabrication of prototype arrays of magnetically coupled microcalorimeters (MMCs) using multiple niobium layers of buried wiring. In order to successfully scale MMCs to large arrays, so that the stray inductance of the wiring is sufficiently low and the sensor meander coil inductance is sufficiently high, the meander coil pitch is decreased. We have investigated linewidths as narrow as 400 nm. Fabricated devices have demonstrated high critical currents of 30 mA for the narrowest pitch.

We describe a small-scale demonstration of an X-ray microcalorimeter using metallic magnetic calorimeters (MMCs) that consist of superconducting meander-shaped sensor coils with very fine pitches. These devices are being developed for potential future astrophysics missions, such as Lynx. Because Lynx requires more than 100 000 pixels on a pitch of around 50 μm, the pixels and array designs are challenging to fabricate. We have fabricated prototype superconducting Nb meander coils with pitches of 0.8, 1.2, 1.6, and 5.0 μm to determine the most optimal geometry for coupling the MMC magnetization signal to the SQUIDs used to read them out. The Nb sensor coils and microstrip wiring are buried beneath the surface of a planarized silicon wafer. There are four buried Nb layers, and these are connected through superconducting Nb vias. We have observed a large critical current of ~ 30 mA for pixels with the finest pitch meander, which have a Nb width of 0.4 μm. We have characterized each pixel geometry from the magnetization, heat capacity, and thermal conductance measurements. The preliminary measured energy resolution from pixels in these geometries is also discussed.

Lynx is an x-ray telescope, one of four large satellite mission concepts currently being studied by NASA to be a flagship mission. One of Lynx's three instruments is an imaging spectrometer called the Lynx x-ray microcalorimeter (LXM), an x-ray microcalorimeter behind an x-ray optic with an angular resolution of 0.5 arc sec and ∼2 m2 of area at 1 keV. The LXM will provide unparalleled diagnostics of distant extended structures and, in particular, will allow the detailed study of the role of cosmic feedback in the evolution of the Universe. We discuss the baseline design of LXM and some parallel approaches for some of the key technologies. The baseline sensor technology uses transition-edge sensors, but we also consider an alternative approach using metallic magnetic calorimeters. We discuss the requirements for the instrument, the pixel layout, and the baseline readout design, which uses microwave superconducting quantum interference devices and high-electron mobility transistor amplifiers and the cryogenic cooling requirements and strategy for meeting these requirements. For each of these technologies, we discuss the current technology readiness level and our strategy for advancing them to be ready for flight. We also describe the current system design, including the block diagram, and our estimate for the mass, power, and data rate of the instrument.

Integrated photonic technologies for quantum applications are discussed with emphasis on those supporting trapped-ion-based systems. A long-term vision of a fully integrated trapped- ion chip and current work towards its realization are presented.

I discuss MIT Lincoln Laboratory’s development of integrated photonics and detectors for trapped-ion-array optical clocks, as well as compact, narrow-linewidth lasers to serve as clock oscillators. These technologies will help enable liter-scale, high- performance optical clocks.

The REgolith X-ray Imaging Spectrometer (REXIS) instrument on board NASA's OSIRIS-REx mission to the asteroid Bennu is a Class-D student collaboration experiment designed to detect fluoresced X-rays from the asteroid's surface to measure elemental abundances. In July and November 2019 REXIS collected ~615 hours of integrated exposure time of Bennu's sun-illuminated surface from terminator orbits. As reported in Hoak et al. (2021), the REXIS data do not contain a clear signal of X-ray fluorescence from the asteroid, in part due to the low incident solar X-ray flux during periods of observation. To support the evaluation of the upper limits on the detectable X-ray signal that may provide insights for the properties of Bennu's regolith, we present an overview of the REXIS instrument, its operation, and details of its in-flight calibration on astrophysical X-ray sources. This calibration includes the serendipitous detection of the transient X-ray binary MAXI J0637-430 during Bennu observations, demonstrating the operational success of REXIS at the asteroid. We convey some lessons learned for future X-ray spectroscopy imaging investigations of asteroid surfaces., Comment: 36 pages, 18 figures, accepted for publication in Space Science Reviews

A germanium charge-coupled device (CCD) offers the advantages of a silicon CCD for X-ray detection – excellent uniformity, low read noise, high energy resolution, and noiseless on-chip charge summation – while covering an even broader spectral range. Notably, a germanium CCD offers the potential for broadband X-ray sensitivity with similar or even superior energy resolution than silicon, albeit requiring lower operating temperatures (≤ 150K) to achieve sufficiently low dark noise due to the lower band gap of this material. The recent demonstration of high-quality gate dielectrics on germanium with low surface-state density and low gate leakage is foundational for realization of high-quality imaging devices on this material. Building on this advancement, MIT Lincoln Laboratory has been developing germanium CCDs for several years, with design, fabrication, and characterization of kpixel-class front-illuminated devices discussed recently. In this article, we describe plans to scale these small arrays to megapixel-class imaging devices with performance suitable for scientific applications. Specifically, we discuss our efforts to increase charge-transfer efficiency, reduce dark current, improve fabrication yield, and fabricate backside-illuminated devices with excellent sensitivity.

Lynx is an x-ray telescope that is one of four large satellite mission concepts currently being studied by NASA to be the next flagship mission. One of Lynx’s three instruments is the Lynx X-ray Microcalorimeter (LXM), an imaging spectrometer placed at the focus of an x-ray optic with 0.5 arc-second angular resolution and approximately 2 m2 area at 1 keV. It will be used for a wide variety of observations, and the driving performance requirements are met through different sub-regions of the array. It will provide an energy resolution of better than 3 eV over the energy range of 0.2 to 7 keV, with pixels sizes that vary in scale from 0.5 to 1 arc-seconds in the inner 5 arc-minute field-of-view, and to 5 arc-seconds in the extended 20 arc-minute field-of-view. The Main Array consists mostly of 1 arc-second pixels in the central 5 arc-minutes with less than 3 eV energy resolution (FWHM) in the energy range of 0.2 to 7 keV. It is enhanced in the inner 1 arc-minute region with 0.5 arc-second pixels that will better sample the point spread function of the X-ray optic. The inner 5 arc-minute region is designed specifically for the observations related to cosmic feedback studies, investigating the interactions of AGN with the local regions surrounding them. The 0.5" pixel size allows detailed studies of winds and jets on a finer angular scale. It is also optimized for spatially resolved measurements of cluster cores. The outer regions of the array are designed to operate during a completely different set of observations. The Extended Array will be utilized for surveys over large regions of the sky, the 20 arc-minute field-of-view making it practical to make observations of the soft diffuse emission from larger scale-structure such as extended galaxies, the outer regions of galaxy groups and clusters and also cosmic filaments. This array is optimized for high energy resolution up to 2 keV through the use of thin (0.5 um) gold absorbers. The Ultra-High-Res Array is designed specifically to enable the study turbulent line broadening around individual through the study of the highly ionized oxygen lines. It is optimized for energy resolution for the oxygen VII and VIII lines, with better than 0.4 eV energy resolution. In this paper we present the design of the baseline configuration and the scientific motivation. We discuss the technologies that are being developed for this instrument, in particular the transition-edge sensor (TES) and metallic magnetic calorimeter (MMC) sensor technologies. We place these technologies in the context of the required energy resolution, energy range, pixel size, and count-rate, as well as strategies for the pixel layout and wiring. We will discuss the use of microwave SQUIDs, HEMT amplifiers, and parametric amplifiers for the read-out and the implications for the cryogenic design. We also describe the design of the full instrument, including the strawman cryogenic design, as well as an estimate for the mass, power and data rate.

We describe recent advances in backside passivation of large-format charge-coupled devices (CCDs) fabricated on 200- mm diameter wafers. These CCDs utilize direct oxide bonding and molecular-beam epitaxial (MBE) growth to enable high quantum efficiency in the ultraviolet (UV) and soft X-ray bands. In particular, the development of low-temperature MBE growth techniques and oxide bonding processes, which can withstand MBE processing, are described. Several highperformance large-format CCD designs were successfully back-illuminated using the presented process and excellent quantum efficiency (QE) and dark current are measured on these devices. Reflection-limited QE is measured from 200 nm to 800 nm, and dark current of less than 1e- /pixel/sec is measured at 40°C for a 9.5 μm pixel.

Silicon charge-coupled devices (CCDs) are commonly utilized for scientific imaging in wavebands spanning the near infrared to soft X-ray. These devices offer numerous advantages including large format, excellent uniformity, low read noise, noiseless on-chip charge summation, and high energy resolution in the soft X-ray band. By building CCDs on bulk germanium, we can realize all of these advantages while covering an even broader spectral range, notably including the short-wave infrared (SWIR) and hard X-ray bands. Since germanium is available in wafer diameters up to 200 mm and can be processed in the same tools used to build silicon CCDs, large-format (>10 MPixel, >10 cm2 ) germanium imaging devices with narrow pixel pitch can be fabricated. Furthermore, devices fabricated on germanium have recently demonstrated the combination of low surface state density and high carrier lifetime required to achieve low dark current in a CCD. At MIT Lincoln Laboratory, we have been developing germanium imaging devices with the goal of fabricating large-format CCDs with SWIR or broadband X-ray sensitivity, and we recently realized our first front-illuminated CCDs built on bulk germanium. In this article, we describe design and fabrication of these arrays, analysis of read noise and dark current on these devices, and efforts to scale to larger device formats.

One option for the detector technology to implement the Lynx x-ray microcalorimeter (LXM) focal plane arrays is the metallic magnetic calorimeter (MMC). Two-dimensional imaging arrays of MMCs measure the energy of x-ray photons by using a paramagnetic sensor to detect the temperature rise in a microfabricated x-ray absorber. While small arrays of MMCs have previously been demonstrated that have energy resolution better than the 3 eV requirement for LXM, we describe LXM prototype MMC arrays that have 55,800 x-ray pixels, thermally linked to 5688 sensors in “hydra” configurations, and that have sensor inductance increased to avoid signal loss from the stray inductance in the large-scale arrays when the detectors are read out with microwave superconducting quantum interference device multiplexers, and that use multilevel planarized superconducting wiring to provide low-inductance, low-crosstalk connections to each pixel. We describe the features of recently tested MMC prototype devices and simulations of expected performance in designs opti- mized for the three subarray types in LXM.

Nitride-based semiconductors have received considerable attention during the last decade due to their outstanding properties for optoelectronic, high frequency, and high power applications. The integration of GaN and Si (100) devices on the same chip would enable a vast array of new applications, from novel power distribution schemes in Si microsystems, to power digital-toanalog converters and new opportunities for optoelectronic devices integrated on a Si platform. This paper aims to summarize some of the recent results on the heterogeneous integration of GaN and Si (100) devices and circuits by using a hybrid 4" wafer bonding technology.

Silicon X-ray detectors often require blocking filters to mitigate noise and out-of-band signal from UV and visible backgrounds. Such filters must be thin to minimize X-ray absorption, so direct deposition of filter material on the detector entrance surface is an attractive approach to fabrication of robust filters. On the other hand, the soft (E OD 6) care must be taken to prevent light from entering the sides and mounting surfaces of the detector. Our methods have been used to deposit filters on the detectors of the REXIS instrument scheduled to fly on OSIRIS-ReX later this year.

Analog & digital circuits implemented in a dual threshold voltage (VT) p-channel organic technology are presented. The dual VT organic technology is compatible with large-area and mechanically flexible substrates due to its low processing temperature (≤ 95°C) and scalable patterning techniques. We demonstrate the first analog & digital organic integrated circuits produced by a dual-gate metal process. The analog circuits are powered by a 5-V supply and include a differential amplifier and a two-stage uncompensated operational amplifier (op-amp). A dynamic comparator is measured to have an input offset voltage of 200 mV and latching time of 119 ms. Both the comparator and the op-amp dissipate 5 nW or less. Area-minimized digital logic is presented. Inverters powered by a 3-V supply were measured to have positive noise margins and consumed picowatts of power. An 11-stage ring oscillator, also powered by a 3-V supply, swings near rail to rail at 1.7 Hz. These results demonstrate dual threshold voltage process feasibility for large-area flexible mixed-signal organic integrated circuits.

A fully photolithographic dual threshold voltage (VT) organic thin-film transistor (OTFT) process suitable for flexible large-area integrated circuits is presented. The nearroom-temperature (

GaN-based semiconductors are excellent candidates for power devices at high frequencies due to their combination of large band gap (3.4 eV), and high electron mobility (1500 ~ 2000 cm/Vs) of the two-dimensional electron gas (2DEG). Current gain cut-off frequencies (fT) in excess of 160 GHz and power gain cut-off frequencies (fmax) of 300 GHz have been demonstrated [1], and RF transistors capable of more than 10 W/mm of output power at 40 GHz has been reported [2]. This power density is almost one order of magnitude higher than in any other semiconductor technology at these frequencies. In this paper we aim to demonstrate that wafer bonding can further expand GaN capabilities. It offers unprecedented freedom in the heterogeneous integration of GaN and other semiconductors, and allows novel device structures.

The effects of bias stress in integrated pentacene organic transistors are studied and modeled for different stress conditions. It is found that the effects of bias stress can be expressed in terms of the shift in applied gate voltage ?V for a given current. An empirical equation describing ?V in terms of different gate and drain bias stress measurements and stress times is presented and verified. In the measured devices, ?V saturates at 14 V, independent of the gate bias-stress condition. A model based on carrier trapping rate equation that accounts for this ?V saturation is developed. The model suggests that the ?V saturation is due to the small density of traps compared to the channel carrier density.

This letter demonstrates a new technology for the heterogeneous integration of GaN and Si devices, which is scalable at least up to 4-in wafers and compatible with conventional Si fabrication. The key step in the proposed technology is the fabrication of a Si (100)-GaN-Si hybrid wafer by bonding a silicon (100) on insulator (SOI) wafer to the nitride surface of an AlGaN/GaN on Si (111) wafer. A thin layer of silicon oxide is used to enhance the bonding between the SOI and the AlGaN/GaN wafers. Using this technology, Si pMOSFETs and GaN high-electron-mobility transistors have been fabricated on a 4-in hybrid wafer. Due to the high-temperature stability of GaN as well as the high-quality semiconductor material resulting from the transfer method, these devices exhibit excellent performance. A hybrid power amplifier has been fabricated as a circuit demonstrator, which shows the potential to integrate GaN and Si devices on the same chip to enable new performance in high-efficiency power amplifiers, mixed signal circuits, and digital electronics.

Directly deposited optical-blocking filters (DD OBFs) have the potential to improve filter performance and lower risk and cost for future x-ray imaging spectroscopy missions. However, they have not been fully characterized on high-performance charge coupled devices (CCDs). This paper reports the results of DD OBFs processed on high-performance photon-counting CCDs. It is found that CCD performance is not degraded by deposition of such filters. X-ray and optical transmission through the OBF is characterized and found to match theoretical expectation. Light-leaks through pinholes and the side and back surfaces are found to lower the optical extinction ratio; various coating processes are developed to resolve these issues.

Germanium exhibits high sensitivity to short-wave infrared (SWIR) and X-ray radiation, making it an interesting candidate for imaging applications in these bands. Recent advances in germanium processing allow for high-quality charge-coupled devices (CCDs) to be realized in this material. In this article, we discuss our evaluation of germanium as an absorber material for CCDs via fabrication and analysis of discrete devices such as diodes, metal-insulator-semiconductor capacitors, and buried-channel metal-oxide-semiconductor field-effect transistors (MOSFETs). We then describe fabrication of our first imaging device on germanium, a 32 × 1 × 8.1 μm linear shift register. Based on this work, we find that germanium is a promising material for CCDs imaging in the SWIR and X-ray bands.

This letter presents a method to fabricate thin-body N-face GaN-on-insulator-on-Si (100) wafers. These new wafers are promising to increase the carrier confinement and reduce the contact resistance in AlGaN/GaN high electron mobility transistors (HEMTs). In the reported technology, a Ga-face AlGaN/GaN epilayer grown on Si (111) is transferred to a Si (100) wafer by direct wafer bonding and thinned down by selective dry etch to the device active layers. A GaN channel thickness as thin as 20 nm is obtained with the use of AlGaN etch-stop layers. Excellent transport characteristics are obtained in the fabricated thin-body N-face AlGaN/GaN structures, with a sheet resistance of 430 Ω/sq, an electron mobility of 1700 cm2/V · s, and a 2-D electron gas concentration of 9 × 1012 cm-2. HEMTs fabricated on these N-face thin-body epilayers shows excellent current-voltage characteristics and great potential for high-frequency applications.

United States. National Aeronautics and Space Administration. Strategic Astrophysics Technology Program (Grant NNX12AF22G)

We report our progress toward optimizing backside-illuminated silicon PIN CMOS devices developed by Teledyne Imaging Sensors (TIS) for far-UV planetary science applications. This project was motivated by initial measurements at Southwest Research Institute (SwRI) of the far-UV responsivity of backside-illuminated silicon PIN photodiode test structures described in Bai et al., SPIE, 2008, which revealed a promising QE in the 100-200 nm range as reported in Davis et al., SPIE, 2012. Our effort to advance the capabilities of thinned silicon wafers capitalizes on recent innovations in molecular beam epitaxy (MBE) doping processes. Key achievements to date include: 1) Representative silicon test wafers were fabricated by TIS, and set up for MBE processing at MIT Lincoln Laboratory (LL); 2) Preliminary far-UV detector QE simulation runs were completed to aid MBE layer design; 3) Detector fabrication was completed through the pre-MBE step; and 4) Initial testing of the MBE doping process was performed on monitoring wafers, with detailed quality assessments. Early results suggest that potential challenges in optimizing the UV-sensitivity of silicon PIN type CMOS devices, compared with similar UV enhancement methods established for CCDs, have been mitigated through our newly developed methods. We will discuss the potential advantages of our approach and briefly describe future development steps.

The Si substrate of GaN-on-Si wafers offers new opportunities to increase the functionality and performance of nitride-based devices. This paper will review three examples of these new devices/systems. First, GaN-on-Si substrates allow the on-chip heterogeneous integration of GaN and Si electronics. Second, the easy removal of the Si substrate through dry or wet etching gives access to the N-face of the GaN layer, and all the new device structures that this orientation enables. Finally, the use of Si substrates for the growth of GaN high voltage switches makes the cost of these devices competitive with Si devices, and the total or partial etch of Si brings a new degree of freedom to increase the breakdown and performance of GaN transistors.

For the first time, we demonstrate control of organic thinfilm transistor's (OTFT) threshold voltage (V T ) by modifying the gate work function. We present a near-room-temperature, fully lithographic process to fabricate integrated pentacene dual V T OTFTs suitable for large-area and flexible mixed signal circuits. Platinum and aluminum are used as the gate metals for the high V T (more depletion-like) and low V T (more enhancement-like) p-channel devices, respectively. The availability of a high V T device enables area-efficient zero-VGS current source loads. We demonstrate positive noise margin inverters which use pico Watts of power and a 3 V supply. Compared to a single V T implementation, the dual V T inverter occupies an area that is 30x smaller, and is 17x faster. These results show that p-channel only organic technologies can produce functional and low-power circuits without integrating a complementary device.

We report our progress toward optimizing backside-illuminated silicon P-type intrinsic N-type complementary metal oxide semiconductor devices developed by Teledyne Imaging Sensors (TIS) for far-ultraviolet (UV) planetary science applications. This project was motivated by initial measurements at Southwest Research Institute of the far-UV responsivity of backside-illuminated silicon PIN photodiode test structures, which revealed a promising QE in the 100 to 200 nm range. Our effort to advance the capabilities of thinned silicon wafers capitalizes on recent innovations in molecular beam epitaxy (MBE) doping processes. Key achievements to date include the following: (1) representative silicon test wafers were fabricated by TIS, and set up for MBE processing at MIT Lincoln Laboratory; (2) preliminary far-UV detector QE simulation runs were completed to aid MBE layer design; (3) detector fabrication was completed through the pre-MBE step; and (4) initial testing of the MBE doping process was performed on monitoring wafers, with detailed quality assessments.

During phase I, two main areas of the tunable filter were investigated intensively. The first and the most important subject was increasing the tunability of the LPG based filter device in order to enable tuning over the required wavelength range (>50nm, in C-band). The second was how to create a tunable filter device with acceptable strength and narrow bandwidth for 100 GHz DWDM applications. Tunability over a range of 50nm was successfully demonstrated during this period with the parallel configuration with electro-optic polymer composites containing nanosized ZnS crystallites. For fabricating filter device, the direct writing of the LPG through the etched optical fiber with ITO layer coated was successfully achieved. This technique eliminates the several critical uncertainties such as peak shifting coming due to chemical etching of the fibers and the peak shifting resulting from the ITO coating. Together with this approach, considerable effort was made to determine the optimal conditions of LPG writing (such as the grating period, grating length and cladding layer thickness) to yield a strong stable spectral transmission peak in the C-band.

Electronic energy disorder associated within amorphous and polycrystaline molecular organic thin film structures strongly affects the macroscopic observable behavior of organic field effect transistors (OFET) and poses practical challenges to implementing OFET circuits. It has been convenient to ignore the detailed physical processes associated with this disorder and model OFET behavior as equivalent to silicon FETs, but such simplifications limit our ability to develop integrated circuit technology as they fail to predict the true integrated OFET behavior. This talk will highlight the evolution of the organic electronic circuit technology and the challenges that lay ahead, emphasizing the need for physically accurate models of device behavior as the cornerstone of any future circuit advancements.

An incoherent correlator system for star pattern recognition and tracking was described by Kouris et al. in SPIE Vol. 4734, as part of the 2002 OPR XIII Conference Session. The experimental demonstration described utilized small but discrete bulk mirrors as the specialised matched filtering elements. The replacement of the discrete bulk mirrors by a matrix of MEMS mirrors is desirable, especially in space applications, due to the light weight, compact size, low power consumption and precise patterning of MEMS structures. We describe here the relation of MEMS mirror parameters to star tracker performance. Two approaches to fabricate a two dimensional array of large area, high tilt angle and fast switching MEMS mirrors with orthogonal tilt axes are discussed, as required in the star tracker application. A preliminary design and test results of the MEMS array are presented.