Originally derided as scientifically erroneous, the Doppler effect is now a vital tool in all aspects of technology, ranging from microscopic to galactic. Doppler, back in the day – and now The explanation of the Doppler effect is almost intuitive to us, with our understanding of wave phenomena along with available frequency sources and measurement […]
The Doppler effect: From highly ridiculed to absolutely indispensable, Part 1
Originally derided as scientifically erroneous, the Doppler effect is now a vital tool in all aspects of technology, ranging from microscopic to galactic. Engineers are familiar with many “effects” ranging from widely used ones such as the piezoelectric effect to somewhat lesser-known ones such as the RF skin effect and even less-familiar ones such as […]
Satellite-based search-and-rescue, Part 4: Enhancements, even the moon
A sophisticated satellite-based system allows pinpointing a person’s location in a dangerous, isolated situation on land or sea. It thus hopefully speeds their subsequent rescue in many cases. This final part looks at the next generation of system satellites and some ideas for a similar lunar system. The MEOSAR satellites The most recent enhancement to […]
Satellite-based search-and-rescue, Part 3: Space segment and satellites
A sophisticated satellite-based system allows pinpointing a person’s location in a dangerous, isolated situation on land or sea. It thus hopefully speeds their subsequent rescue in many cases. Cospas-Sarsat uses three types of satellites: low-Earth orbit search-and-rescue (LEOSAR), medium-Earth orbit search-and-rescue (MEOSAR), and high-altitude geosynchronous orbit search-and-rescue (GEOSAR satellites). There are five LEOSAR, seven GEOSAR, […]
Satellite-based search-and-rescue, Part 2: Ground segment and transmitter beacons
A sophisticated satellite-based system allows pinpointing a person’s location in a dangerous, isolated situation on land or sea. It thus hopefully speeds their subsequent rescue in many cases. Over one million emergency beacons are in use worldwide, all operating at 406 MHz (with some exceptions, called out below). Cospas-Sarsat does not manufacture or sell beacons. […]
Satellite-based search-and-rescue, Part 1: The overall system
A sophisticated satellite-based system allows pinpointing a person’s location in a dangerous, isolated situation on land or sea. It thus hopefully speeds their subsequent rescue in many cases. You’ve undoubtedly seen or read stories about someone miraculously recused at sea or in some relatively uninhabited, remote part of the Earth, without a way to call […]
Reaction wheels ensure satellites maintain the right attitude: Part 2
Electrically driven reaction wheels use conservation of angular momentum to keep a satellite pointed in the right direction, eliminating the need for fuel-powered and limited thrusters. Part 1 was an introduction to reaction wheel basics. This part continues the investigation into their performance and construction. Physics and analysis Although the basic principle of reaction wheels […]
Reaction wheels ensure satellites maintain the right attitude: Part 1
Electrically driven reaction wheels use conservation of angular momentum to keep a satellite pointed in the right direction, eliminating the need for fuel-powered and limited thrusters. Orbiting satellites usually must maintain a precise and stable orientation for various reasons: to keep their cameras or radar pointed at their Earth targets or to keep their telescopes […]
Automobile Hands-Off Detection, Part 4: Capacitive solutions
Cars with lane-keeping assistance (LKA) also are mandated to have a hands-off detection (HOD) function; there are several ways to meet this challenging requirement. Despite the BOM advantages of torque-based HOD, it has performance issues. Capacitive-based sensing is a viable alternative approach. Capacitive sensing for HOD monitors the driver’s grip on the steering wheel by […]
Automobile Hands-Off Detection, Part 3: Torque solutions
Cars with lane-keeping assistance (LKA) also are mandated to have a hands-off detection (HOD) function; there are several ways to meet this challenging requirement. The previous part of this article discussed the need for hands-off (or on) detection (HOD) and its connection to the lane-keeping assistance feature in today’s cars. This part will look at […]
