We are designing a telescope imaging system based on an apodized diffractive optical element called an apodized photon sieve (APS) in order to detect exoplanets. APSs are orders of magnitude less massive, lightweight and more compactable than mirrors. Proposed imaging system can be installed on any telescope as an "attachment" or used as a telescope itself as a part of a CubeSat payload. Methods were developed for designing the apodized sieves, measuring PSFs, and characterizing high-contrast performance of the imaging system. This new kind of APS has rotational symmetry and provides high-contrast (up to 10-10 levels) in all directions with just one image with the throughput of 40% or higher.
Photon sieves for generating and identifying beams with orbital angular momentum are presented. They are diffractive optical elements (DOEs) based on a traditional Fresnel zone plate (FZP), but composed of a series of microscopic pinholes usually centered on the bright zones. Each circular hole contributes to the focusing and there are multiple possibilities for applying pupil apodization to DOEs that are not possible, and/or difficult, and/or costly compared to optical systems with conventional lenses and mirrors. We will describe in detail the basic spiral photon sieve as well as how various types of the photon sieves can be combined into one optical element for spatial beam shaping.
The US Air Force Academy of Physics has built FalconSAT-7, a membrane solar telescope to be deployed from a
3U CubeSat in LEO. The primary optic is a 0.2m photon sieve – a diffractive element consisting of billions of tiny
circular dimples etched into a Kapton sheet. The membrane its support structure, secondary optics, two imaging
cameras and associated control, recording electronics are packaged within half the CubeSat volume. Once in space
the supporting pantograph structure is deployed, extending out and pulling the membrane flat under tension. The
telescope will then be directed at the Sun to gather images at H-alpha for transmission to the ground. We will
present details of the optical configuration, operation and performance of the flight telescope which has been made
ready for launch in early 2017.
There is a need for small Sense and Avoid (SAA) systems for small and micro Unmanned Aerial Systems (UAS) to
avoid collisions with obstacles and other aircraft. The proposed SAA systems will give drones the ability to “see” close
up and give them the agility to maneuver through tight areas. Doppler radar is proposed for use in this sense and avoid
system because in contrast to optical or infrared (IR) systems Doppler can work in more harsh conditions such as at
dusk, and in rain and snow. And in contrast to ultrasound based systems, Doppler can better sense small sized obstacles
such as wires and it can provide a sensing range from a few inches to several miles. An SAA systems comprised of
Doppler radar modules and an array of directional antennas that are distributed around the perimeter of the drone can
cover the entire sky. These modules are designed so that they can provide the direction to the obstacle and
simultaneously generate an alarm signal if the obstacle enters within the SAA system’s adjustable “Protection Border”.
The alarm signal alerts the drone’s autopilot to automatically initiate an avoidance maneuver. A series of Doppler radar
modules with different ranges, angles of view and transmitting power have been designed for drones of different sizes
and applications. The proposed Doppler radar micro SAA system has simple circuitry, works from a 5 volt source and
has low power consumption. It is light weight, inexpensive and it can be used for a variety of small unmanned aircraft.
FalconSAT-7 (FS-7), a 3U CubeSat solar telescope, is the first-ever on-orbit demonstration of a lightweight deployable membrane primary optic that is twice the size of the host spacecraft. The telescope payload consists of the deployment structure, optical, electronic subsystems and occupying 1.5 U, while the rest of the volume is used for the bus, including satellite power, control, communications with the ground, etc. The deployment subsystem provides membrane deployment, positioning and tension with high precision for proper imaging, while the optical subsystem includes secondary optics with a camera to record images of the Sun at H-alpha. The electronics subsystem is used to control the primary optics deployment, focusing, image storage and transfer to the bus etc. We conducted an end-to-end flight optical subsystem test and a series of tests of the corrosion of the photon sieve due to atomic oxygen. The flight model build will be completed by October 2015with a launch date set for September 2016.
Revolutionary new fly eye radar sensor technologies based on an array of directional antennas is eliminating the
need for a mechanical scanning antenna or complicated phase processor. Proposed sense and avoid radar based on
fly eye radar technology can be very small, provides continuous surveillance of entire sky (360 degree by azimuth
and elevation) and can be applied for separate or swarm of micro/nano UAS or UGS. Monopulse technology
increases bearing accuracy several folds and radar can be multi-functional, multi-frequency. Fly eye micro-radars
are inexpensive, can be expendable. Prototype of sense and avoid radar with two directional antennas has been
designed and bench tested.
The USAF Academy Department of Physics has built FalconSAT-7, a membrane solar telescope to be deployed from a 3U CubeSat in LEO. The primary optic is a 0.2m photon sieve - a diffractive element consisting of billions of tiny circular dimples etched into a Kapton sheet. The membrane, its support structure, secondary optics, two imaging cameras and associated control/recording electronics are all packaged within half the CubeSat volume. Once in space, the supporting pantograph structure is deployed, extending out and pulling the membrane flat under tension. The telescope will then be directed at the Sun to gather images at H-alpha for transmission to the ground. Due for launch in 2015, FalconSAT-7 will serve as a pathfinder for future surveillance missions consisting of a 0.3m aperture deployed from a 12U satellite. Such a telescope would be capable of providing sub-meter resolution of ground-based objects.
The USAF Academy Department of Physics is building FalconSAT-7, a membrane solar telescope to be deployed from a 3U CubeSat in LEO. The primary optic is a 0.2m photon sieve.—a diffractive element consisting of billions of tiny holes in an otherwise opaque polymer sheet. The membrane, its support structure, secondary optics, two imaging cameras and associated control/recording electronics are all packaged within half the CubeSat volume. Once in space the supporting pantograph structure is deployed, pulling the membrane flat under tension. The telescope will then be steered towards the Sun to gather images at H-alpha for transmission to the ground. Due for launch in 2016, FalconSAT-7 will serve as a pathfinder for future surveillance missions.
To compensate for its eye’s inability to point its eye at a target, the fly’s eye consists of multiple angularly spaced sensors giving the fly the wide-area visual coverage it needs to detect and avoid the threats around him. Based on a similar concept a revolutionary new micro-radar sensor technology is proposed for detecting and tracking ground and/or airborne low profile low altitude targets in harsh urban environments. Distributed along a border or around a protected object (military facility and buildings, camp, stadium) small size, low power unattended radar sensors can be used for target detection and tracking, threat warning, pre-shot sniper protection and provides effective support for homeland security. In addition it can provide 3D recognition and targets classification due to its use of five orders more pulses than any scanning radar to each space point, by using few points of view, diversity signals and intelligent processing. The application of an array of directional antennas eliminates the need for a mechanical scanning antenna or phase processor. It radically decreases radar size and increases bearing accuracy several folds. The proposed micro-radar sensors can be easy connected to one or several operators by point-to-point invisible protected communication. The directional antennas have higher gain, can be multi-frequency and connected to a multi-functional network. Fly eye micro-radars are inexpensive, can be expendable and will reduce cost of defense.
We describe imaging capabilities of a 0.2 m membrane diffractive primary (DOE) used as a key element in FalconSat-7, a space-based solar telescope. Its mission is to take an image of the Sun at the H-alpha wavelength (656nm) over a narrow bandwidth while in orbit. In this case the DOE is a photon sieve which consists of billions of tiny holes, with the focusing ability dependent on an underlying Fresnel zone geometry. Uniform radial expansion/contraction of the substrate due to temperature or relative humidity change will result in a shift in focal length without introducing errors in phase of the transmitted wavefront and without a decrease in efficiency. We will also show that while ideally the DOE surface should be held flat to within 5.25 microns, an opto-mechanical analysis showed that local deformations up to 32 microns are possible without significantly degrading the image quality.
This paper focuses on recent progress in designing FallconSAT-7, a 33U CubeSat solar telescope designed to image the Sun from low Earth orbit. The telescope system includes a deployable structure that supports a membrane photon sieve under tension as well as secondary optics. To satisfy mission requirements to demonstrate diffraction limited imaging capability of this collapsible, f/2 diffractive primary we have completed studying a number off effects on membrane material that can affect system imaging quality.
There are two switching processes where observe in polymer-dispersed liquid crystals (PDLC) when pulse electric field applied: - Slow switching process with rise time hundreds microseconds; - Fast switching process with nanoseconds rise time. The result of research, design and testing ultra-fast PDLC optical gate is presented. The feasibility of 100 nsec rise time optical gate with 1 square inch crystal clear transmission (better than 1.54 dB) and attenuation in OFF state more than 26 dB (30.4 dB for two serial layers) for non-polarized light has been shown.
We are currently constructing FalconSAT-7 for launch in mid-2014. The low-Earth, 3U CubeSat solar telescope
incorporates a 0.2m deployable membrane photon sieve with over 2.5 billion holes. The aim of the experiment is to
demonstrate diffraction limited imaging of a collapsible, diffractive primary over a narrow bandwidth. As well as being
simpler to manufacture and deploy than curved, polished surfaces, the sheets do not have to be optically flat, greatly
reducing many engineering issues. As such, the technology is particularly promising as a means to achieve extremely
large optical primaries from compact, lightweight packages.
Holographic optical elements have found many applications in imaging systems, optical wireless communication, data
storage etc. We have developed filter for Lidar receiver which includes holographic optical elements (HOEs) - volume
diffraction grating (VDG) and holographic lens. HOEs were designed and recorded to meet system requirements.
Wide dynamic range gating photosensor modules has been design for LIDAR-RADAR applications on base R7400U
(active area 8 mm. diameter) R7600U (active area 18x18 mm.) Hamamatsu photomultiplier tubes. The photomultiplier
tubes R7400U, series have two kinds of photocathode: low resistance semitransparent multialkali photocathodes and
semitransparent bialkali photocathodes with large resistance. Different kinds of photocathodes require different approach
to gating circuits design. High-speed pulse gating (gating rise time 10 nsec, setting time 40 nsec for 99%) has been used
for enhancing of target contrast at ocean optic application for both kinds: semitransparent bialkali and semitransparent
multialkali photocathodes. Wide dynamic range (50 dB of optical power) has been achieved by optimizing of applied to
dynodes voltages. Compression up to 30 dB has been used for following output signal digital processing. Hamamatsu
photosensitive modules were used in the two system receivers in pulsed LIDAR system. The system was mounted on
the bow of the R/V New Horizon and collected data from August 25 thru September 8, 2005 as part of the LOCO field
test in Monterey Bay. Approximately 4 million LIDAR profiles were collected during this period. During the field test
the profiles were processed to show relative changes in water optical properties and to reveal water column structure in
New approach to high-speed detection and modulation based on application of capacitance modulation is offered. Application of capacitance modulation allows to increase sensitivity and noise immunity of high-speed photodetectors in microwave range.
Subject: INTEVAC hybrid photomultiplier vacuum tube IPD-280 with 18 mm GaAsP photocathode, imaging electron optics, ion trap and 0.5, 1.0 diameter Schottky barrier anode.
Problem: Large area intensified photodiodes (IPDs) have parameters (high sensitivity, gain, speed of operation, bandwidth, low noises), which are ideal for Ocean optic applications. However, these IPDs have not enough dynamic range and lifetime.
Target of objective investigation: Identify the cause for small dynamic range and short lifetime of IPDs and optimize them for Ocean Optic applications.
The voltages applied to photocathode and focusing electrodes have been experimentally optimized for maximal IPD sensitivity,dynamic range, pulse rise, and transit time. The photoelectrons trajectories and ions have been simulated using SIMION 3D 7,0 software for various voltages applied to the focusing electrodes. The uniformity of the photocathode has been tested to determine the impact of ions on the photocathode. Electron and ion currents investigations have been made for both negative and positive voltages applied to the ion trap electrode. Optimizing the regime for electron focusing and minimizing the ion current impact to photocathode was determines as result of the investigation. Reducing the voltages applied to photocathode and focusing the electrodes from 8 KV to 4-6 KV decreased the ion current. In this regime, the gain of IPD does not decrease significantly and the rise time and transit time of IPD remined practically the same.