Monthly Archives: August 2016

View of Jupiter From Satellite Metis

The arrival of the Juno spacecraft at Jupiter has motivated me to take a look a closer look at the Jovian system. I was surprised to see that we have cataloged 67 moons, sixteen of which have been discovered since 2003 and are not yet named. One moon that was new to me is called Metis (Figure 2), which is Jupiter's innermost moon. It is very tiny and resides within Jupiter's main ring. Continue reading

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Age of Presidents at Inauguration

I was crawling around the Wikipedia looking for presidential information, and I found a list of the ages of the US presidents ordered from oldest to youngest. I threw Hillary Clinton and Donald Trump into the list (Table 1) to see where they would place – they are old by historic standards. In fact, Donald Trump would be the oldest ever. Continue reading

Posted in History Through Spreadsheets, Personal | 4 Comments

Asteroid Size Estimation

I often see announcements of Near-Earth Objects (NEOs) in the scientific press. For asteroids, these announcements are usually accompanied by a size estimate of the asteroid. In this post, I will discuss a commonly used formula for the effective spherical diameter of an asteroid based on its normalized brightness (i.e. absolute magnitude). Continue reading

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Calculating a Parameter's Worst-Case Range

Many electronic systems are required to generate an alarm when they detect their power failing – the alarm is referred to as a "dying gasp". These systems are required to generate a dying gasp alarm when their input voltage drops below a specified level. Continue reading

Posted in Electronics | 3 Comments

The Tyranny of the Spreadsheet Cell

I had a conversation the other day with an engineer to whom I was expressing my frustrations with using Excel to process large data sets of complex numbers. She also has processed large data sets with Excel and commented that she found the processing painful. I told her about how I was using Excel to work with my data sets, but my techniques all seemed contrived and overly complex. While you can use Excel to work with these data sets, it is a bit like trying to use a Swiss Army knife as a screwdriver. Yes, it can turn a screw but there are much better ways! Continue reading

Posted in software | 8 Comments

Asteroid Impact Damage Estimate

I have seen a number of articles in the popular scientific press about asteroid 1997 XF11 and the close approach it made to Earth back in June. The June approach was not that close – ~27 million kilometers. The closest approach is expected in 2028 and will be 980,000 km or 2.4 times the average Earth-Moon distance. Continue reading

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Planetary Atmosphere Leakage

I have always been interested in the fact that some planets have atmospheres and others do not. At the time of formation, planets have a primary atmosphere that consists largely of light elements (hydrogen and helium) – Earth has a secondary atmosphere formed outgassing from tectonic activity and comet impact residue. For small bodies, these low-molecular weight elements escape into space. I had never looked at how these gases escaped until I recently found a Wikipedia article about how gases escape from planetary atmospheres (e.g. Figure 1), and the math and physics involved were too enticing to pass up. Continue reading

Posted in Astronomy | 2 Comments

Fiber Optic Cable and Lightning

Lightning is a tough problem. All of my personal electronic systems are well grounded and have the best surge protection I can buy. Yet I still suffer occasional losses due to lightning – for example, this weekend I replaced a surge-blown power adapter at my cabin in northern Minnesota. Intuitively, you would think that fiber optic systems should be better protected against lightning strikes than copper-based systems because glass fiber does not conduct electricity. This is not necessarily true. Continue reading

Posted in Fiber Optics | 4 Comments