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NASA NTRS1998

The Athena Mars Rover Science Payload

The Mars Surveyor missions that will be launched in April of 2001 will include a highly capable rover that is a successor to the Mars Pathfinder mission's Sojourner rover. The design goals for this rover are a total traverse distance of at least 10 km and a total lifetime of at least one Earth year. The rover's job will be to explore a site in Mars' ancient terrain, searching for materials likely to preserve a record of ancient martian water, climate, and possibly biology. The rover will collect rock and soil samples, and will store them for return to Earth by a subsequent Mars Surveyor mission in 2005. The Athena Mars rover science payload is the suite of scientific instruments and sample collection tools that will be used to perform this job. The specific science objectives that NASA has identified for the '01 rover payload are to: (1) Provide color stereo imaging of martian surface environments, and remotely-sensed point discrimination of mineralogical composition. (2) Determine the elemental and mineralogical composition of martian surface materials. (3) Determine the fine-scale textural properties of these materials. (4) Collect and store samples. The Athena payload has been designed to meet these objectives. The focus of the design is on field operations: making sure the rover can locate, characterize, and collect scientifically important samples in a dusty, dirty, real-world environment. The topography, morphology, and mineralogy of the scene around the rover will be revealed by Pancam/Mini-TES, an integrated imager and IR spectrometer. Pancam views the surface around the rover in stereo and color. It uses two high-resolution cameras that are identical in most respects to the rover's navigation cameras. The detectors are low-power, low-mass active pixel sensors with on-chip 12-bit analog-to-digital conversion. Filters provide 8-12 color spectral bandpasses over the spectral region from 0.4 to 1.1 micron Narrow-angle optics provide an angular resolution of 0.28 mrad/pixel, nearly a factor of four higher than that of the Mars Pathfinder and Mars Surveyor '98 cameras. Image compression will be performed using a wavelet compression algorithm. The Mini-Thermal Emission Spectrometer (Mini-TES) is a point spectrometer operating in -the thermal IR. It produces high spectral resolution (5 /cm) image cubes with a wavelength range of 5-40 gm, a nominal signal/noise ratio of 500:1, and a maximum angular resolution of 7 mrad (7 cm at a distance of 10 in). The wavelength region over which it operates samples the diagnostic fundamental absorption features of rockforming minerals, and also provides some capability to see through dust coatings that could tend to obscure spectral features. The mineralogical information that Mini-TES provides will be used to select from a distance the rocks and soils that will be investigated in more detail and ultimately sampled. Mini-TES is derived from the MO/MGS TES instrument, but is significantly smaller and simpler. The instrument uses an 8-cm Cassegrain telescope, a Michelson interferometer, and uncooled pyroelectric detectors. Along with its mineralogical capabilities, Mini-TES can provide information on the thermophysical properties of rocks and soils. Viewing upward, it can also provide temperature profiles through the martian atmospheric boundary layer. Elemental and Mineralogical Composition: Once promising samples have been identified from a distance using Pancam/Mini-TES, they will be studied in detail using up to three compositional sensors that can be placed directly against them by an Instrument Arm. The two compositional sensors, presently on the payload are an Alpha-Proton-X-Ray Spectrometer (APXS), and a Mossbauer Spectrometer. The APXS is derived closely from the instrument that flew on Mars Pathfinder. Radioactive alpha sources and three detection modes (alpha, proton, and x-ray) provide elemental abundances of rocks and soils to complement and constrain mineralogical data. The Athena APXS will have a revised mechanical design that will cut down significantly on backscattering of alpha particles from martian atmospheric carbon. It will also include a target of known elemental composition that will be used for calibration purposes. The Athena Mossbauer Spectrometer is a diagnostic instrument for the mineralogy and oxidation state of Fe-bearing phases, which are particularly important on Mars. The instrument measures the resonant absorption of gamma rays produced by a Co-57 source to determine splitting of nuclear energy levels in Fe atoms that is related to the electronic environment surrounding them. It has been under development for space flight for many years at the Technical University of Darmstadt. The Mossbauer Spectrometer (and the other arm instruments) will be able to view a small permanent magnet array that will attract magnetic particles in the martian soil. The payload may also include a Raman Spectrometer. If included, the Raman Spectrometer will provide precise identification of major and minor mineral phases. It requires no sample preparation, and is also sensitive to organics. Fine-Scale Texture: The Instrument Arm a also carries a Microscopic Imager that will obtain high-resolution monochromatic images of the same materials for which compositional data will be obtained. Its spatial resolution is 20 micron/pixel over a 1 cm depth of field, and 40 micron/pixel over a 1-cm depth of field. Like Pancam, it uses the same active pixel sensor detectors and electronics as the rover's navigation cameras. The Instrument Arm is a three degree-of-freedom arm that uses designs and components from the Mars Pathfinder and Mars Surveyor '98 projects. Its primary function is instrument positioning. Along with the instruments noted above, it also carries a brush that can be used to remove dust and other loose coatings from rocks. Sample Collection and Storage: Martian rock and soil samples will be collected using a low-power rotary coring drill called the Mini-Corer. An important characteristic of this device is that it can obtain intact samples of rock from up to 5 cm within strong boulders and bedrock, Nominal core dimensions are 8xl7 mm. The Mini-Corer drills a core to the commanded depth in a rock, shears it off, retains it, and extracts it. It can also acquire samples of loose soil, using soil sample cups that are pressed downward into loose material. The Mini-Corer can drill at angles from vertical to 45' off vertical. It has six interchangeable bits for long life. Mechanical damage to the sample during drilling is minimal, and heating is negligible. After acquisition, the sample may be viewed by the arm instruments, and/or placed in one of 104 compartments in the Sample Container. A subset of the acquired samples may be replaced with other samples obtained later if desired. The Sample Container has no moving parts, and is mounted external to the rover for easy removal by the Mars Surveyor 2005 flight system. Operation of the rover will make extensive use of automated onboard navigation and hazard avoidance capabilities. Otherwise, use of onboard autonomy is minimal. Data downlink capability is about 40 Mbit/sol, and the use of the Mars Surveyor '01 orbiter for data relay imposes a limit of at most two command cycles per sol. Because of the significant amount of time available between command cycles, all payload elements will be operated sequentially, rather than in parallel.; this approach also significantly simplifies operations and minimizes peak power usage. The landing site for the '01 rover has not been selected yet. Site selection will make as full use as possible of Mars Global Surveyor data, and will involve substantial input from the broad Mars science community. Summary: The following table describes the mass, power, providers, and key scientific objectives of all the major elements of the Athena payload. Additional Athena payload information may be found at: http://astrosun.tn.cornell.edu/athena/index.html. Additional information contained in the original.

Squyes, S. W.↗

NASA NTRS2011

Scoring Dawg Core Breakoff and Retention Mechanism

This novel core break-off and retention mechanism consists of a scoring dawg controlled by a set of two tubes (a drill tube and an inner tube). The drill tube and the inner tube have longitudinal concentric holes. The solution can be implemented in an eccentric tube configuration as well where the tubes have eccentric longitudinal holes. The inner tube presents at the bottom two control surfaces for controlling the orientation of the scoring dawg. The drill tube presents a sunk-in profile on the inside of the wall for housing the scoring dawg. The inner tube rotation relative to the drill tube actively controls the orientation of the scoring dawg and hence its penetration and retrieval from the core. The scoring dawg presents a shaft, two axially spaced arms, and a tooth. The two arms slide on the control surfaces of the inner tube. The tooth, when rotated, can penetrate or be extracted from the core. During drilling, the two tubes move together maintaining the scoring dawg completely outside the core. After the desired drilling depth has been reached the inner tube is rotated relative to the drill tube such that the tooth of the scoring dawg moves toward the central axis. By rotating the drill tube, the scoring dawg can score the core and so reduce its cross sectional area. The scoring dawg can also act as a stress concentrator for breaking the core in torsion or tension. After breaking the core, the scoring dawg can act as a core retention mechanism. For scoring, it requires the core to be attached to the rock. If the core is broken, the dawg can be used as a retention mechanism. The scoring dawg requires a hard-tip insert like tungsten carbide for scoring hard rocks. The relative rotation of the two tubes can be controlled manually or by an additional actuator. In the implemented design solution the bit rotation for scoring was in the same direction as the drilling. The device was tested for limestone cores and basalt cores. The torque required for breaking the 10-mm diameter limestone cores was 5 to 5.8 lb-in. (0.56 to 0.66 N-m).

Badescu, Mircea↗

NASA NTRS2013

Wireline Deep Drill for the Exploration of Icy Bodies

One of the most pressing current questions in space science is whether life has ever arisen anywhere else in the universe. Water is a critical prerequisite for all life-as-we-know-it, thus the possible exploration targets for extraterrestrial life are bodies that have or had copious liquid: Mars, Europa, and Enceladus. Due to the oxidizing nature of Mars' surface, as well as subsurface liquid water reservoirs present on Europa and Enceladus, the search for evidence of existing life must likely focus on subsurface locations, at depths sufficient to support liquid water or retain biologic signatures. To address these questions, an Auto-Gopher sampler has been developed that is a wireline type drill. This drill is suspended on a tether and its motors and mechanisms are built into a tube that ends with a coring bit. The tether provides the mechanical connection to a rover/lander on a surface as well as power and data communication. Upon penetrating to a target depth, the drill is retracted from the borehole, the core is deposited into a sample transfer system, and the drill is lowered back into the hole. Wireline operation sidesteps one of the major drawbacks of traditional continuous drill string systems by obviating the need for multiple drill sections, which add significantly to the mass and the complexity of the system (i.e. penetration rate was 40 cm per hour). Drilling to 2 meter depth and recovering of cores every 10 cm took a total time of 15 hours (a single step of drilling 10 cm and retrieving the core was 45 minutes). Total energy to reach the 2 m depth was 500 Whr. The Weight on Bit was limited to less than 70 Newton. The core recovery was 100%.

sampling↗

NASA NTRS2003

An Ultrasonic Sampler and Sensor Platform for In-Situ Astrobiological Exploration

The search for existing or past life in the Universe is one of the most important objectives of NASA's mission. In support of this objective, ultrasonic based mechanisms are currently being developed at JPL to allow probing and sampling rocks as well as perform as a sensor platform for in-situ astrobiological analysis. The technology is based on the novel Ultrasonic/Sonic Driller/Corer (USDC), which requires low axial force, thereby overcoming one of the major limitations of planetary sampling in low gravity using conventional drills. The USDC was demonstrated to: 1) drill ice and various rocks including granite, diorite, basalt and limestone, 2) not require bit sharpening, and 3) operate at high and low temperatures. The capabilities that are being investigated including probing the ground to select sampling sites, collecting various forms of samples, and hosting sensors for measuring chemical/physical properties. A series of modifications of the USDC basic configuration were implemented leading an ultrasonic abrasion tool (URAT), Ultrasonic Gopher for deep Drilling, and the lab-on-a-drill.

robotics↗

NASA NTRS2010

Miniature Low-Mass Drill Actuated by Flextensional Piezo Stack

Recent experiments with a flextensional piezoelectric actuator have led to the development of a sampler with a bit that is designed to produce and capture a full set of sample forms including volatiles, powdered cuttings, and core fragments. The flextensional piezoelectric actuator is a part of a series of devices used to amplify the generated strain from piezoelectric actuators. Other examples include stacks, bimorphs, benders, and cantilevers. These devices combine geometric and resonance amplifications to produce large stroke at high power density. The operation of this sampler/drill was demonstrated using a 3x2x1-cm actuator weighing 12 g using power of about 10-W and a preload of about 10 N. A limestone block was drilled to a depth of about 1 cm in five minutes to produce powdered cuttings. It is generally hard to collect volatiles from random surface profiles found in rocks and sediment, powdered cuttings, and core fragments. Toward the end of collecting volatiles, the actuator and the bit are covered with bellows-shaped shrouds to prevent fines and other debris from reaching the analyzer. A tube with a miniature bellows (to provide flexibility) is connected to the bit and directs the flow of the volatiles to the analyzer. Another modality was conceived where the hose is connected to the bellows wall directly to allow the capture of volatiles generated both inside and outside the bit. A wide variety of commercial bellows used in the vacuum and microwave industries can be used to design the volatiles capture mechanism. The piezoelectric drilling mechanism can potentially be operated in a broad temperature range from about-200 to less than 450 C. The actuators used here are similar to the actuators that are currently baselined to fly as part of the inlet funnel shaking mechanism design of MSL (Mars Science Laboratory). The space qualification of these parts gives this drill a higher potential for inclusion in a future mission, especially when considering its characteristics of low mass, small size, low power, and low axial loads for sampling.

Sherrit, Stewart↗

NASA NTRSDate not supplied

Automation and AI in Space Drilling

Future planetary surface sampling missions, such as delving past the near-surface ice layers on Mars in search of organics and possibly signs of past/extant life, will require lightweight, low-mass planetary drilling and sample handling. Unlike terrestrial drills, these exploration drills must work dry (without drilling muds or gas), blind (no prior local or regional seismic or other surveys), and light (very low downward force or weight on bit, and perhaps 100 W available from solar power or batteries). Given the lightspeed transmission delays to Mars and outward, an exploratory planetary drill cannot be controlled directly from Earth. Drills that penetrate deeper than a few centimeters are likely to get stuck if operated open-loop (the MSL drill only penetrates 5 cm, and the MER Rock Abrasion Tools 5 mm by comparison), so some form of local drill control is required. In the relatively near-term, human crews cannot be presumed to be available for surface instrument teleoperation. Therefore highly automated drill and sample-transfer operations will be required, to explore the subsurface with the ability to safe robotic drilling systems and recover and continue on from the most probable fault conditions. Current automation, scheduling and diagnostic approaches will be discussed that roughly track the actions and roles of humans in terrestrial manual drilling operations.

drill automation↗

NASA NTRS2012

Deep Drilling and Sampling via the Wireline Auto-Gopher Driven by Piezoelectric Percussive Actuator and EM Rotary Motor

The ability to penetrate subsurfaces and perform sample acquisition at depths of meters is critical for future NASA in-situ exploration missions to bodies in the solar system, including Mars and Europa. A corer/sampler was developed with the goal of acquiring pristine samples by reaching depths on Mars beyond the oxidized and sterilized zone. To developed rotary-hammering coring drill, called Auto-Gopher, employs a piezoelectric actuated percussive mechanism for breaking formations and an electric motor rotates the bit to remove the powdered cuttings. This sampler is a wireline mechanism that is incorporated with an inchworm mechanism allowing thru cyclic coring and core removal to reach great depths. The penetration rate is being optimized by simultaneously activating the percussive and rotary motions of the Auto-Gopher. The percussive mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) mechanism that is driven by piezoelectric stack and that was demonstrated to require low axial preload. The Auto-Gopher has been produced taking into account the a lessons learned from the development of the Ultrasonic/Sonic Gopher that was designed as a percussive ice drill and was demonstrated in Antarctica in 2005 to reach about 2 meters deep. A field demonstration of the Auto-Gopher is currently being planned with objective of reaching as deep as 3 to 5 meters in tufa subsurface.

Auto-Gopher↗

NASA NTRS2011

Percussive Augmenter of Rotary Drills (PARoD)

A percussive augmenter is being developed and it is designed to add ultrasonic hammering to a conventional commercial rotary drill through an adapter using a piezoelectric actuator. The combination of ultrasonic hammering and rotation creates a drill that requires low power and low axial load while providing faster penetration than conventional rotary-only drills. These characteristics make percussive augmentation of rotary drills ideal for not only planetary exploration but commercial applications as well. The purpose of this internship was to produce, test, and optimize an augmenter that drives a 2 inch diameter bit. This task was part of the percussive augmenter's phase II of an ongoing contract and it involved increasing the capability of the .25 inch version of the augmenter prototype that was developed in phase I. Due to fabrication delays of the augmenter, an extensive part of the test effort was conducted using previous rotary and hammer drill prototypes. These tests focused on drilling deep over long periods of time to provide for effective stress test of the drill. Modifications were made to the drill, its components, and the testing procedure to achieve desired borehole depths. These results were used to start initial testing on the 2 inch augmenter and provide preliminary data on the augmenter's ability to significantly improve penetration rate over conventional rotary-only drills.

rotraty hammer↗

NASA NTRS2014

ROPEC - ROtary PErcussive Coring Drill for Mars Sample Return

The ROtary Percussive Coring Drill is a light weight, flight-like, five-actuator drilling system prototype designed to acquire core material from rock targets for the purposes of Mars Sample Return. In addition to producing rock cores for sample caching, the ROPEC drill can be integrated with a number of end effectors to perform functions such as rock surface abrasion, dust and debris removal, powder and regolith acquisition, and viewing of potential cores prior to caching. The ROPEC drill and its suite of end effectors have been demonstrated with a five degree of freedom Robotic Arm mounted to a mobility system with a prototype sample cache and bit storage station.

Chu, Philip↗

NASA NTRS2011

Praying Mantis Bending Core Breakoff and Retention Mechanism

Sampling cores requires the controlled breakoff of the core at a known location with respect to the drill end. An additional problem is designing a mechanism that can be implemented at a small scale, yet is robust and versatile enough to be used for a variety of core samples. The new design consists of a set of tubes (a drill tube, an outer tube, and an inner tube) and means of sliding the inner and outer tubes axially relative to each other. Additionally, a sample tube can be housed inside the inner tube for storing the sample. The inner tube fits inside the outer tube, which fits inside the drill tube. The inner and outer tubes can move axially relative to each other. The inner tube presents two lamellae with two opposing grabbing teeth and one pushing tooth. The pushing tooth is offset axially from the grabbing teeth. The teeth can move radially and their motion is controlled by the outer tube. The outer tube presents two lamellae with radial extrusions to control the inner tube lamellae motion. In breaking the core, the mechanism creates two support points (the grabbing teeth and the bit tip) and one push point. The core is broken in bending. The grabbing teeth can also act as a core retention mechanism. The praying mantis that is disclosed herein is an active core breaking/retention mechanism that requires only one additional actuator other than the drilling actuator. It can break cores that are attached to the borehole bottom as

Badescu, Mircea↗

NASA NTRS2019

Thermal design of the sample handling assembly in the sampling and caching subsystem on the Mars 2020 rover

The Mars 2020 Rover is scheduled to land on Mars on February 18, 2021. One of the primary mission objectives for the Mars 2020 Rover is to collect a set of Martian regolith samples for potential future return to Earth. Regolith and rock samples will be collected and placed into sample tubes using a coring drill, located at the end of a large Robotic Arm, on the outside of the rover. Filled sample tubes will be transferred from the outside of the Rover into the Adaptive Caching Assembly (ACA), located inside the Rover chassis, via the Bit Carousel. Once the filled sample tube is brought into the ACA, the Sample Handling Assembly (SHA) will transfer it to all of the internal processing stations of the ACA for volume assessment, sealing and finally drop-off on the Martian surface. The ACA is a volume within the rover chassis that is not temperature-controlled. Actuators inside the SHA and its End Effector (EE) must be warmed to above -55°C and -25°C, respectively, prior to use. This paper discusses the thermal design of the SHA that uses heaters and temperature sensors to warm up and maintain the temperature-sensitive arm components within temperature limits during operation. Thermal performance predictions for Mars surface operations are also presented.

Lee, Chern-Jiin↗

NASA NTRS1986

Surface drilling technologies for Mars

We propose rock drilling and coring conceptual designs for the surface activities associated with a manned Mars mission. Straightforward extensions of equipment and procedures used on Earth are envisioned for the sample coring and shallow high explosive shot holes needed for tunneling and seismic surveying. A novel rocket exhaust jet piercing method is proposed for very rapid drilling of shot holes required for explosive excavation of emergency radiation shelters. Summaries of estimated equipment masses and power requirements are provided, and the indicated rotary coring rigs are scaled from terrestrial equipment and use compressed C02 from the Martian atmosphere for core bit cooling and cuttings removal. A mass of 120 kg and power of 3 kW(e) are estimated for a 10 m depth capability. A 100 m depth capacity core rig requires about 1150 kg and 32 kw(e). The rocket exhaust Jet equipment devised for shallow (3m) explosive emplacement shot holes requires no surface power beyond an electrical ignition system, and might have a 15 kg mass.

J D Blacic↗

NASA NTRS2011

Advanced Development of a Compact 5-15 lbf Lox/Methane Thruster for an Integrated Reaction Control and Main Engine Propulsion System

This paper describes the advanced development and testing of a compact 5 to 15 lbf LOX/LCH4 thruster for a pressure-fed integrated main engine and RCS propulsion system to be used on a spacecraft "vertical" test bed (VTB). The ability of the RCS thruster and the main engine to operate off the same propellant supply in zero-g reduces mass and improves mission flexibility. This compact RCS engine incorporates several features to dramatically reduce mass and parts count, to ease manufacturing, and to maintain acceptable performance given that specific impulse (Isp) is not the driver. For example, radial injection holes placed on the chamber body for easier drilling, and high temperature Haynes 230 were selected for the chamber over other more expensive options. The valve inlets are rotatable before welding allowing different orientations for vehicle integration. In addition, the engine design effort selected a coil-on-plug ignition system which integrates a relay and coil with the plug electrode, and moves some exciter electronics to avionics driver board. The engine injector design has small dribble volumes to target minimum pulse widths of 20 msec. and an efficient minimum impulse bit of less than 0.05 lbf-sec. The propellants, oxygen and methane, were chosen because together they are a non-toxic, Mars-forward, high density, space storable, and high performance propellant combination that is capable of pressure-fed and pump-fed configurations and integration with life support and power subsystems. This paper will present the results of the advanced development testing to date of the RCS thruster and the integration with a vehicle propulsion system.

Hurlbert, Eric A.↗

NASA NTRS2006

Active Struts With Variable Spring Stiffness and Damping

An ultrasonic rock-abrasion tool (URAT) was developed using the same principle of ultrasonic/sonic actuation as that of the tools described in two prior NASA Tech Briefs articles: Ultrasonic/ Sonic Drill/Corers With Integrated Sensors (NPO-20856), Vol. 25, No. 1 (January 2001), page 38 and Ultrasonic/ Sonic Mechanisms for Drilling and Coring (NPO-30291), Vol. 27, No. 9 (September 2003), page 65. Hence, like those tools, the URAT offers the same advantages of low power demand, mechanical simplicity, compactness, and ability to function with very small axial loading (very small contact force between tool and rock). Like a tool described in the second of the cited previous articles, a URAT includes (1) a drive mechanism that comprises a piezoelectric ultrasonic actuator, an amplification horn, and a mass that is free to move axially over a limited range and (2) an abrasion tool bit. A URAT tool bit is a disk that has been machined or otherwise formed to have a large number of teeth and an overall shape chosen to impart the desired shape (which could be flat or curved) to the rock surface to be abraded. In operation, the disk and thus the teeth are vibrated in contact with the rock surface. The concentrated stresses at the tips of the impinging teeth repeatedly induce microfractures and thereby abrade the rock. The motion of the tool induces an ultrasonic transport effect that displaces the cuttings from the abraded area. The figure shows a prototype URAT. A piezoelectric-stack/horn actuator is housed in a cylindrical container. The movement of the actuator and bit with respect to the housing is aided by use of mechanical sliders. A set of springs accommodates the motion of the actuator and bit into or out of the housing through an axial range between 5 and 7 mm. The springs impose an approximately constant force of contact between the tool bit and the rock to be abraded. A dust shield surrounds the bit, serving as a barrier to reduce the migration of rock debris to sensitive instrumentation or mechanisms in the vicinity. A bushing at the tool-bit end of the housing reduces the flow of dust into the actuator and retains the bit when no axial load is applied.

Farley, Gary L.↗

NASA NTRS2006

Ultrasonically Actuated Tools for Abrading Rock Surfaces

Dolgin, Benjamin↗

NASA NTRS2007

Circuit and Method for Communication Over DC Power Line

A circuit and method for transmitting and receiving on-off-keyed (OOK) signals with fractional signal-to-noise ratios uses available high-temperature silicon- on-insulator (SOI) components to move computational, sensing, and actuation abilities closer to high-temperature or high-ionizing radiation environments such as vehicle engine compartments, deep-hole drilling environments, industrial control and monitoring of processes like smelting, and operations near nuclear reactors and in space. This device allows for the networking of multiple, like nodes to each other and to a central processor. It can do this with nothing more than the already in-situ power wiring of the system. The device s microprocessor allows it to make intelligent decisions within the vehicle operational loop and to effect control outputs to its associated actuators. The figure illustrates how each node converts digital serial data to OOK 18-kHz in transmit mode and vice-versa in receive mode; though operations at lower frequencies or up to a megahertz are within reason using this method and these parts. This innovation s technique modulates a DC power bus with millivolt-level signals through a MOSFET (metal oxide semiconductor field effect transistor) and resistor by OOK. It receives and demodulates this signal from the DC power bus through capacitive coupling at high temperature and in high ionizing radiation environments. The demodulation of the OOK signal is accomplished by using an asynchronous quadrature detection technique realized by a quasi-discrete Fourier transform through use of the quadrature components (0 and 90 phases) of the carrier frequency as generated by the microcontroller and as a function of the selected crystal frequency driving its oscillator. The detected signal is rectified using an absolute-value circuit containing no diodes (diodes being non-operational at high temperatures), and only operational amplifiers. The absolute values of the two phases of the received signal are then summed and hard limited (digitized) by comparing them to a reference level and are then input into a microprocessor as a serial bit stream. The quasi-discrete Fourier transform is performed in high-temperature components (operational amplifiers, analog switches, resistors, and capacitors). The demodulated signal is a serial data stream that is input to the UART (universal asynchronous receiver transmitter) receiver pin of the microprocessor. The OOK of the carrier frequency uses the output of the UART pin as an enabling signal that drives the gate of the MOSFET. Logic low bits enable the carrier frequency (realized by using the 0 phase signal from the microcontroller, though either phase may be used) to be DC-coupled to the power supply bus through a current-limiting resistor mounted between the MOSFET drain and the supply rail. The presence of logic lows on the power supply rail is realized by carrier bursts while logic highs are realized by the absence of bursts.

Krasowski, Michael J.↗