Category: Electronics in Space

Char and VARCHAR

By , September 5, 2011 8:34 PM

Where the data varies significantly in length from one record to the next with the longest being significantly longer than the average then you need to use a VARCHAR. There is no point in using a CHAR(40) if the average length is only 15 since that will resuult in a lot of wasted space in most records. Using a VARCHAR(40) instead means that you can still fit the leng 40 chharacter values while the average space used will be 15 plus the record length marker overhead.

summary use varchar for variable length fields and use char if you are expecting it to always be the same eg CHAR (ASSS, DASS, FASS, TASS) this is good for a char ie fixed length fields

Moon pics

By , July 23, 2011 4:42 PM

Hi see pics

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Rad Hardening

By , September 14, 2009 3:23 AM

When your computer behaves erratically, mauls your data, or just “crashes” completely, it can be frustrating. But for an astronaut trusting a computer to run navigation and life-support systems, computer glitches could be fatal.

Unfortunately, the radiation that pervades space can trigger such glitches. When high-speed particles, such as cosmic rays, collide with the microscopic circuitry of computer chips, they can cause chips to make errors. If those errors send the spacecraft flying off in the wrong direction or disrupt the life-support system, it could be bad news.

To ensure safety, most space missions use radiation hardened computer chips. “Rad-hard” chips are unlike ordinary chips in many ways. For example, they contain extra transistors that take more energy to switch on and off. Cosmic rays can’t trigger them so easily. Rad-hard chips continue to do accurate calculations when ordinary chips might “glitch.”

NASA relies almost exclusively on these extra-durable chips to make computers space-worthy. But these custom-made chips have some downsides: They’re expensive, power hungry, and slow — as much as 10 times slower than an equivalent CPU in a modern consumer desktop PC.

With NASA sending people back to the moon and on to Mars–see the Vision for Space Exploration–mission planners would love to give their spacecraft more computing horsepower.

Having more computing power onboard would help spacecraft conserve one of their most limited resources: bandwidth. The bandwidth available for beaming data back to Earth is often a bottleneck, with transmission speeds even slower than old dial-up modems. If the reams of raw data gathered by the spacecraft’s sensors could be “crunched” onboard, scientists could beam back just the results, which would take much less bandwidth.

Objects, particularly spacecraft structures, antennas, solar arrays and other spacecraft equipment,  are shielded against damage from momentary exposure to high energy electromagnetic radiation in the form of high energy optical (laser) radiation or nuclear radiation by a radiation barrier or shield constructed of fibrous silica refractory composite material like that used for the heat shield tiles on the shuttle spacecraft.

Major radiation damage sources

Typical sources of exposure of electronics to ionizing radiation are solar wind and the Van Allen radiation belts for satellites, nuclear reactors in power plants for sensors and control circuits, residual radiation from isotopes in chip packaging materials, cosmic radiation for both high-altitude airplanes and satellites, and nuclear explosions for potentially all military and civilian electronics.

  • Cosmic rays come from all directions and consist of approx. 85% protons, 14% alpha particles, and 1% heavy ions, together with ultraviolet radiation and x-rays. Most effects are caused by particles with energies between 108 and 2*1010 eV, though there are even particles with energies up to 1020 eV. The atmosphere filters most of these, so they are primarily a concern for high-altitude applications like stratospheric jets and satellites.
  • Solar particle events come from the direction of the sun and consist of a large flux of high-energy (several GeV) protons and heavy ions, again accompanied with UV and x-ray radiation. They cause a scale of problems for satellites, ranging from radiation damage to loss of altitude by heating up the upper regions of the atmosphere, causing them to raise up, and decelerating the low-orbit satellites by friction.
  • Van Allen radiation belts contain electrons (up to about 10 MeV) and protons (up to 100s MeV) trapped in the geomagnetic field. The particle flux in the regions farther from the Earth can vary wildly depending on the actual conditions of the sun and the magnetosphere. Due to their position they pose a concern for satellites.
  • Secondary particles result from interaction of other kinds of radiation with structures around the electronic devices.
  • Chip packaging materials were an insidious source of radiation that was found to be causing soft errors in new DRAM chips in the 1970s. Traces of radioactive elements in the packaging of the chips were producing alpha particles, which were then occasionally discharging some of the capacitors used to store the DRAM data bits. These effects have been reduced today by using purer packaging materials, and employing error-correcting codes to detect and often correct DRAM errors.

Comms

By , September 13, 2009 6:09 AM

Communication modules

Radiation-Hardened, High-Data-Rate Ka-Band Modulator and Transmitter

Technology Details
NASA requires that all future “near-Earth” missions (near-Earth defined as any spacecraft within one million kilometers of Earth) requiring more than 10 MHz of downlink data bandwidth operate in the 25.5 to 27.0 GHz band. Developed for NASA’s Solar Dynamics Observatory mission and adapted for the Lunar Reconnaissance Orbiter mission, this spaceflight
transmitter meets and/or exceeds all of NASA’s performance requirements and is the first to be designed for Ka-band.
How it works
This design consists of a phase-locked oscillator; a high-bandwidth, QPSK vector modulator; a medium-power, Ka-band solid-state power amplifier, a highly efficient DC-DC converter; and radiation-hardened, high-rate driver circuitry that receives I and Q channel data. The radiation-hardened design enables the Ka-band communications downlink system to transmit
130 Mbps of data (300 Msps after data encoding) to the ground system. The low error vector magnitude of the modulator reduces the implementation loss of the transmitter in which it is used, thereby increasing the overall communication system link margin.
Why it is better
Prior high-rate transmitters exist for X-band (~8 GHz) and Ku-band (~15 GHz), but those can’t take advantage of the Ka-band frequencies. This new Ka-band transmitter and modulator offer several unique design features that improve upon the current state of the art and enable the use of this high-frequency radio band. One design element that sets this technology apart is its unique packaging scheme and mechanical design that creates a compact, back-to-back cavity enclosure that utilizes die attach, substrate attach, wire bonding, and conventional surface mount technologies.

Thomas Challenger Thomas Challenger