Duncan Steel

Duncan Steel is based in Nelson but works for the Xerra Earth Observation Institute with its HQ in Alexandra. He has worked in space research for almost forty years, with times spent with NASA, ESA, various universities and observatories, and also running his own company. Duncan is the author of four books, over a hundred research papers, and more than a thousand articles for newspapers and magazines. He has also appeared in hundreds of radio and TV programmes. Minor planet/ asteroid (4713) Steel is named for him, as is a lunar-roving robot in one of Arthur C. Clarke's SciFi novels.

Happy New Year (and a missed Easter) - Out of Space

Mar 25, 2019

As I write it is March 25th, which was the date of New Year in Great Britain and its colonies until 1752. Indeed, throughout history it was a common date for the start of the civil year in a wide range of European states and principalities, being the traditional date of the vernal equinox, and so the beginning of the seasonal year. On top of that notable calendrical event, yesterday (March 24th) seems to have slipped by without people recognising that according to the mnemonic (Easter is the first Sunday after the first full moon after the vernal equinox) it should have been the date of Easter, if strict astronomy were followed. Here I explain why it was not (the date of Easter this year).  Being a bit of a tragic when it comes to calendars, I must … Read More

Does Earth have a natural prime meridian? - Out of Space

Mar 20, 2019

We are generally habituated to using the Greenwich meridian as the global standard for mapping and time-keeping, despite it being only 135 years since its adoption. As I show here, if the Catholic Church had adopted in 1582 a more-precise calendar in terms of year length then a natural prime meridian results, in a location that might appear surprising. My apologies for posting a new blog so soon after the previous one, but there’s something I need to communicate today. One could say that time is of the essence. Just how true those five words are will soon, I hope, become apparent as you read this piece. Why today? Well, today’s Google Doodle gives a clue:  Google being a US-based company, you’ll notice that it says ‘Fall Equinox 2019’. They mean ‘Autumn’ of course, but at … Read More

On the Shoulders of Giants? - Out of Space

Mar 16, 2019

Isaac Newton is often thought to be the inventor of the apparently self-deprecating phrase ‘If I have seen further it is by standing on the shoulders of giants’, but he was not: actually it had been in use for over 500 years before he repeated it in 1675. Of more significance is that Newton wrote it in a letter to one of his great scientific rivals… who may have been a hunchbacked dwarf.  Friday afternoons generally bring the welcomed arrival of an email from the Science Media Centre (although today – the dreaded Ides of March – also brought terrible news from Christchurch; thoughts with the victims, their friends and families). That email, containing the weekly ‘Science Deadline’ news in science and technology, generally contains some pithy quote. So here is what appeared in the latest issue … Read More

New Zealand from Space - Out of Space

Mar 11, 2019

The European Space Agency’s current Earth observation image of the week features New Zealand in all its glory. Let us take it as read that NZ is a beautiful, breathtaking country. Myriad artistic renditions and simple tourist snaps bear witness to that, but it is also truly an amazing sight when seen from high above, by satellites in orbit. Although Europe is half the world away, it’s clear that staff with the European Space Agency (ESA) agree, with NZ being made the subject of this week’s Earth observation image of the week featuring a composite panorama made from data collected by the Sentinel-3A satellite in August last year.     And here it is the complete image: New Zealand as it appeared on 2018 August 22 in imagery collected by the Sentinel-3A satellite passing about … Read More

Space Station and docked Dragon capsule visible throughout NZ - Out of Space

Mar 04, 2019

As I write, the Dragon capsule – a spacecraft intended to loft US astronauts into orbit – has been docked with the Space Station for almost 18 hours on its initial test flight. It happens that you will be able to see the station plus capsule passing over New Zealand each evening for the next week or so, before the Dragon detaches to return to Earth on Saturday.  The International Space Station (ISS) is visible again from throughout New Zealand, but now it is slightly brighter than previously because it currently has the new SpaceX Crew Dragon capsule docked with it. If you were to visit the NASA website that deals with the International Space Station, at the moment the latest news reads as follows: SpaceX Crew Dragon Successfully Docks to Station After making 18 orbits of Earth … Read More

The Visibility of the Space Station - Out of Space

Feb 22, 2019

The International Space Station (and many other satellites) can easily be viewed passing overhead using the naked eye, so long as you know when to look, and where. But why  can we see it, and how does it return so often?  In a blog post a few days ago I presented tables of times when the International Space Station (ISS ) could be spotted from fourteen different towns/cities in New Zealand through until the last day of the month, and it should be easy enough for anyone to estimate the viewing opportunities from anywhere else in NZ using those tables. The calculations were made using the Heavens-Above website, and I also mentioned a NASA website from which email alerts can be obtained automatically, telling you when the ISS can be seen from your location. Since then David Gibb … Read More

Times to Spot the Space Station - Out of Space

Feb 19, 2019

It’s easy to see the International Space Station passing overhead: you just need to know when and where to look. Oh, and a clear sky. The International Space Station (ISS) regularly passes across New Zealand, a little more than 400 km above our heads – rather less than the distance between Auckland and Wellington. Most of these transits occur either in daytime, making the ISS difficult (though not impossible) to see against the sky, or in the depths of night, when it is dark because it is in Earth’s shadow. Every so often, however, the geometry is right and the ISS can be seen in the dark sky either in the evening or the morning, after sunset or before sunrise; whilst down below we are in darkness, the ISS in orbit may still be illuminated by sunlight, making … Read More

The Nelson bush fire: What can satellite images tell us about such events? - Out of Space

Feb 12, 2019

The ongoing fires in the Nelson-Tasman region have quite rightly provoked much alarm. The response of Fire and Emergency New Zealand, the NZ Police, the NZ Defence Force, and many private individuals, has been magnificent. However, the utilisation of satellite imagery for assessing such fires and then planning and responding is deficient in NZ compared to much of the rest of the developed world, where such information is used as a matter of course. In the post below I illustrate what can be done… and my own mistakes.    I remember once reading a letter to the editor of The Times in which the correspondent lamented that Latin was no longer taught at most schools. He told the tale of having once erred whilst driving, almost colliding with another car which had the right of way, and he wound down … Read More

Satellite imagery of the Nelson bush fire - Out of Space

Feb 09, 2019

The area burnt in the ongoing bush fire in the Nelson-Tasman region, largely around Pigeon Valley near Wakefield, can easily be seen in satellite imagery collected in recent days.  Earth observation satellites frequently cross New Zealand and, clouds allowing, collect imagery of the land and sea below. In later posts I will discuss such data collection in more detail, but the specific intent of this post is to make easily available some imagery showing the area burnt in the ongoing Nelson-Tasman bush fire. There are many potential free sources of satellite imagery, though of course one needs to know where to access the data, and how to process the images in order to get your desired results. I have been doing such things for some years, and so am well-practised, but downloading and massaging the imagery so as to be … Read More

Satellite Orbits: Global Navigation Systems - Out of Space

Feb 05, 2019

Apart from the US-provided Global Positioning System (GPS) used by most commercial navigation systems – such as in your car, or mobile phone – there are several distinct networks operated by other space agencies deploying their own satellite fleets. Here I describe the orbits employed by the Russian, European Union and Chinese GNSS constellations. (Part 3 in a series of posts concerning satellite orbits.)   My previous post concerned the US Global Positioning System (GPS), which uses a constellation of at least 24 satellites (currently 31 operational) to provide worldwide high-precision positional location. This is the GNSS (Global Navigation Satellite System) that many of us use daily in our mobile electronic devices. There are other satellite fleets that have been assembled to deliver the same sort of service, however, and in the present blog post I will … Read More