Things Are Looking Brighter! But Not The Stars

October 11, 2021 by Bob Baddeley 37 Comments

Growing up in Montana I remember looking out at night and seeing the Milky Way, reminding me of my insignificance in the universe. Now that I live in a city, such introspection is no longer easy, and like 1/2 of humanity that also lives in urban areas, I must rely on satellites to provide the imagery. Yet satellites are part of the problem. Light pollution has been getting worse for decades, and with the recent steady stream of satellite launches and billionaire joyrides we have a relatively new addition to the sources of interference. So how bad is it, and how much worse will it get?

Looking up at the night sky, you can usually tell the difference between various man-made objects. Planes go fairly slowly across the sky, and you can sometimes see them blinking green and red. Meteors are fast and difficult to see. Geostationary satellites don’t appear to move at all because they are orbiting at the same rate as earth’s rotation, while other orbit types will zip by.

SpaceX has committed to reducing satellite brightness, and some observations have confirmed that new models are a full magnitude darker, right at the threshold of naked-eye observation. Unfortunately, it’s only a step in the right direction, and not enough to satisfy astronomers, who aren’t looking up at the night sky with their naked eyes, naturally.

The satellites aren’t giving off the light themselves. They are merely reflecting the light from the sun back to the earth, exactly the same way the moon is. Thus something that is directly in the shadow of the Earth will not reflect any light, but near the horizon the reflection from the satellites can be significant. It’s not practical to only focus our observatories in the narrow area that is the Earth’s shadow during the night, so we must look closer to the horizon and capture the reflections of the satellites. Continue reading “Things Are Looking Brighter! But Not The Stars” →

Robust I2C And SPI In Space Thanks To Bus Isolation

September 29, 2021 by Lewin Day 28 Comments

Imagine you’re sending a piece of hardware to space on a satellite. Unless you’re buddy-buddy with NASA, it’s pretty unlikely you’ll ever be able to head up there and fix something if it goes wrong once it’s launched. Robust design is key, so that even in the event of a failure in one component, the rest of the hardware can keep working.

The example I2C isolation circuit from [Max’s] paper. The SPI implementation is even simpler.

[Max Holliday] found himself in this exact situation, running 69 I2C and SPI devices in a single satellite. Thus, he came up with circuits to auto-isolate devices from these buses in the event of an issue. That work is the subject of a research paper now available on the TechRxiv Preprint Server.

The problem is that these simple buses aren’t always the most robust, being vulnerable to single-point failures where one bad part takes down other parts of the bus. [Max] notes that vast numbers of sensors and devices rely on these standards, and it can be difficult or prohibitively expensive to design without them, so a solution was needed.

To fix this, [Max] developed a simple external circuit that could be placed on each node of a I2C or SPI communication bus. In the event of malfunction, that node can be cut off from the bus by this circuit, allowing the rest of the system to go on functioning.

With little more than a few transistors, MOSFETs and passives, you too could protect your buses from malfunctions using these techniques. [Max] did just that on the NASA V-R3x mission which flew successfully in January 2021 if you needed any further confirmation of the value of this technique.

It’s something that won’t bother the home hobbyist building a garage door opener, but it could be of great value to those designing systems that must fail gracefully if they fail at all. Be sure to share your best tips and tricks for robust SPI and I2C buses in the comments below!

Hurricane Hunting From Outer Space

September 27, 2021 by Al Williams 8 Comments

If you live in the right part of the world, you spend a lot of the year worried about hurricanes or — technically — tropical cyclones. These storms carry an amazing amount of power and can change your life. However, we are relatively spoiled these days compared to the past. It is hard to imagine, but there was a time when a hurricane’s arrival was something of a mystery. Sure, ships would report what they encountered, but finding exact data about a hurricane was a bit hit or miss. We often talk about space technology making life better. Weather forecasting — especially for tropical storms — is one place where money spent in space has made life much better on Earth.

The lack of data about storms can be fatal. The Great Galveston hurricane of 1900 took around 12,000 lives. It might have had a better outcome, but forecasters missed where the storm was heading, announcing that it would go from Cuba to Florida which was just totally wrong. Not that a forecaster couldn’t make a mistake today, but with aircraft and satellite coverage, you’d know very quickly that the prediction was wrong and you’d sound the alarm. In truth, the prediction models have become very good over the years, so the chances of this happening today are virtually nil in any event. But being able to precisely locate and track storms helps reduce the impact of the storm and also feeds data into the models that makes them even more accurate for the future.

Continue reading “Hurricane Hunting From Outer Space” →

Review: Hands On With The Swarm Satellite Network Eval Kit

September 7, 2021 by Al Williams 29 Comments

If you have devices out in the field, you probably want to connect with them. There was a time when that was hard to do, requiring telephone wires or specialized radio gear. Now cellular data is prevalent, but even cellular isn’t everywhere. If you have the cash, you can pay a number of satellite companies to carry your data, but that’s generally pricey and has its own challenges.

The age of satellite constellations is changing that. Of course everyone by now has heard of Starlink which is offering satellite internet via numerous satellites that are much smaller than traditional telecom satellites. But they’re not the only came in town.

A company called Swarm has put up a constellation of 1/4U cube satellites in low orbits. They offer a ground station that uses an omni antenna and a subscription access program for small amounts of data. They sent us a unit to review, and while I haven’t used the system in a real project yet, the kit was pretty impressive.

About Swarm

Swarm tile device — The Swarm Tile is made to mount on a PCB

The Swarm “tile” is a tiny radio that can talk bi-directionally with small satellites in low Earth orbit. The little unit is made to mount on a PCB, can control its power consumption, and talks to your system via a standard 3.3V UART connection. It does, however, require a small antenna and maybe even a smaller antenna for its GPS module. Small, in this case, is about a mid-size handy talkie antenna. There is a half-wave antenna that doesn’t need a ground plane and a shorter antenna that does need a ground plane.

Continue reading “Review: Hands On With The Swarm Satellite Network Eval Kit” →

A Satellite Upconverter Need Not Be Impossible To Make

July 31, 2021 by Jenny List 8 Comments

Those readers whose interests don’t lie in the world of amateur radio might have missed one of its firsts, for the last year or two amateurs have had their own geostationary satellite transponder. Called Es’hail-2 / AMSAT Phase 4-A / Qatar-OSCAR 100, it lies in the geostationary orbit at 25.9° East and has a transponder with a 2.4 GHz uplink and a 10.489 GHz downlink. Receiving the downlink is possible with an LNB designed for satellite TV, but for many hams the uplink presents a problem. Along comes [PY1SAN] from Brazil with a practical and surprisingly simple solution using a mixture of odd the shelf modules and a few hand-soldered parts.

An upconverter follows a simple enough principle, the radio signal is created at a lower frequency (in this case by a 435 MHz transmitter) and mixed with a signal from a local oscillator. A filter then picks out the mixer product — the sum of the two — and amplifies it for transmission. [PY1SAN]’s upconverter takes the output from the transmitter and feeds it through an attenuator to a MiniCircuits mixer module which takes its local oscillator via an amplifier from a signal generator module. The mixer output goes through a PCB stripline filter through another amplifier module to a power amplifier brick, and thence via a co-ax feeder to a dish-mounted helical antenna.

The whole thing is a series of modules joined by short SMA cables, and could probably be largely sourced from a single AliExpress order without too much in the way of expenditure. It’s by no means easy to get on air via Es’hail-2, but at least now it need not be impossibly expensive. Even the antenna can be made without breaking the bank.

We covered Es’hail-2 when it first appeared. May it long provide radio amateurs with the chance to operate worldwide with homebrew microwave equipment!

Continue reading “A Satellite Upconverter Need Not Be Impossible To Make” →

StarLink Terminal Unit Firmware Dumped

July 7, 2021 by Al Williams 17 Comments

There’s a lot of expense in what telephone companies call “the last mile” — delivering service from the main trunks to your home or business. StarLink wants to avoid that cost by connecting you via an array of low-orbit satellites and some users are already using the service. In Belgium, [Lennert Wouters] managed to dump the terminal’s firmware and has some interesting observations.

The teardown is actually more than just a firmware dump. His “level 1” teardown involves exposing the board. This can be tricky because there are apparently different versions of the terminal out already, so advice from one source might not match your hardware, and that was the case here.

Continue reading “StarLink Terminal Unit Firmware Dumped” →

You Have About Four Months To Find A Lost Satellite

June 13, 2021 by Jenny List 10 Comments

In the annals of technical achievement originating from the United Kingdom there lies a forgotten success story that should have led to greater things but instead became a dead-end even before it had happened. We’re referring of course to Prospero, a British satellite that holds the honour of being the only one to have been launched on board a British-developed satellite launch platform. On the 28th of October 1971 it was launched aboard a Black Arrow rocket from the Woomera launch site in Australia and successfully entered orbit to complete its mission. When it was launched the Black Arrow program had already been canceled by the British government, with the launch proceeding only because rocket and satellite were by then already on the pad.

So the Brits became the sixth nation to develop a satellite launch capability, and promptly canned it. Prospero was a success though and remains in orbit, and was even re-activated periodically as late as the 1990s. With its fiftieth anniversary approaching in October we think it’s worth looking for to mark the occasion, and so would like to remind you of its existence and the impending anniversary. If any community can find a lost satellite, hear its call if it is still transmitting anything, and maybe even wake it up, it’s you lot. Hackaday readers never cease to amaze us with their talents, and we know that among you will be people with what it takes to find Prospero.

To help you along your way there’s a lot of information about the satellite to be found online, including the details of an unsuccessful attempt to contact it a decade ago for the anniversary in 2011, and a real-time tracker to help you find its position. Maybe some of you have a decent enough telescope to take a snap of it as it passes over, but if a radio signal could be retrieved from it that would be particularly impressive. Watch out though, you might find yourself hearing an Orbcomm satellite on the same frequency.

So if any of you fancy firing up your SDRs and pointing an antenna skywards over the next few months, we’d like to hear about your progress. It’s possible that the craft may by now be incapable of life, but if anything can be found it’s worth a try.

This isn’t the first satellite rescue attempt documented here on Hackaday. A few years back we put out the call to rescue ICE/ISEE-3.