A Quick And Easy Tape Measure Turnstile Antenna For MILSAT Snooping

June 30, 2023 by Dan Maloney 16 Comments

The number of satellites whizzing by over our heads at any moment is staggering, and growing at a rapid rate as new constellations are launched. But sometimes it’s the old birds that are the most interesting, as is the case with some obsolete but still functional military communications satellites, which thanks to a lack of forethought are largely unsecured and easily exploitable. And all that’s needed to snoop in on them is a cheap ham radio and something like this simple and portable satcom antenna.

As proof of the global nature of the radio hobby, the design in the video below by Brit [Tech Minds] borrows heavily from previous work by Italian ham [Ivo Brugnera (I6IBE)], which itself was adapted to use 3D-printed parts in a German blog post a few years ago. The common thread is the use of tape measures for the elements of the aptly named turnstile antenna, a tried and true material for lightweight, foldable antennas that amateur radio enthusiasts have been using for years. The antenna is similar in design to the classic three-element Yagi-Uda, with a crossed pair of driven elements in the middle of a boom that also supports a reflector and a director. Strips of tape measure material are held to the 20-mm aluminum tubing boom with 3D-printed brackets. A phasing harness of precisely cut coax cable connects to the driven elements and runs down the boom; the quarter-wavelength loop serves to introduce the 90° phase shift needed for the circularly polarized signal from the satellites.

A quick scan with a vector antenna analyzer showed just how well this antenna performs on the 220-MHz band, and the antenna was easily able to pick up the Brazilian satellite pirate’s chatter. The tape measure elements make the antenna easy to handle and foldable, not to mention pretty cheap to build. And what’s not to love about that?

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Methane-Tracking Satellites Hunt For Nasty Greenhouse Gas Emissions

May 30, 2023 by Lewin Day 41 Comments

Much of the reporting around climate change focuses on carbon dioxide. It’s public enemy number one when it comes to gases that warm the atmosphere, as a primary byproduct of fossil fuel combustion.

It’s not the only greenhouse gas out there, though. Methane itself is a particularly potent pollutant, and one that is being emitted in altogether excessive amounts. Satellites are now on the hunt for methane emissions in an attempt to save the world from this odorless, colorless gas.

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South Korea Successfully Sends Satellites To Orbit

May 30, 2023 by Chris Lott 8 Comments

South Korea’s KARI ( Korea Aerospace Research Institute ) successfully put a commercial satellite into orbit Thursday, achieving another milestone in their domestic space program. The Nuri rocket (aka KLSV-2) left the Naro Space Center launch pad on the southern coast of the peninsula at 18:24 KST, after a communications glitch in the pad’s helium tank facility caused a one-day slip. The primary payload was the 180 kg refrigerator-sized Earth observation satellite NEXTSat-2. It uses synthetic aperture radar (SAR) and also has instruments to observe neutrons in near-Earth orbit due to the impact of solar activity on cosmic radiation. In addition, seven CubeSats were successfully deployed:

Justek JLC-101-V1.2, to verify satellite orbital control system
Lumir, measuring cosmic radiation and testing rad-hardened microprocessor design
Cairo Space, weather observation and space debris technology demonstration
KASI-SAT (Korea Astronomy and Space Science Institute) SNIPE, actually four nano-sats which will achieve a 500 km – 600 km polar orbit and fly in formation to measure plasma variations.

It seems that SNIPE-C, Justek, and Lumir are having communication troubles and may be lost. Ground controllers are still searching. This launch comes almost one year after the previous launch of a dummy satellite in June, which we wrote about last year.

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ESA Juice’s RIME Antenna Breaks Free After Some Jiggling And Percussive Action

May 13, 2023 by Maya Posch 22 Comments

After ESA’s Jupiter-bound space probe Juice (Jupiter Icy Moons Explorer) launched on April 14th of this year, it initially looked as if it had squeezed out a refreshingly uneventful deployment, until it attempted to unfurl its solar panels and antennae. One of these antennae, for the RIME (Radar for Icy Moons Exploration) instrument that uses ice-penetrating radar to get a subsurface look at Jupiter’s moons, ended up being rather stuck. Fortunately, on May 12th it was reported that ESA engineers managed to shock the sticky pin loose.

Release of the jammed antenna coinciding with the actuation of the NEA ('NEA 6 Release'). The antenna wobbles about before settling in a locked position. (Credit: ESA) — Release of the jammed antenna coinciding with the actuation of the NEA (‘NEA 6 Release’). The antenna wobbles about before settling in a locked position. (Credit: ESA)

We previously covered the discovery of Juice’s RIME antenna troubles, with one of the retaining pins that hold the antenna in place in its furled position stubbornly refusing to shift the few millimeters that would have allowed for full deployment. Despite the high-tech nature of the Juice spacecraft, the optimal solution to make the pin move was simply to try and shake it loose.

Attempts were initially made using the spacecraft’s thrusters to shake the whole vehicle, as well as by warming it in sunlight. Each of these actions seemed to help a little bit, but the breakthrough came when a non-explosive actuator (NEA) was actuated in the jammed bracket. This almost fully fixed the problem, leading the team in charge to decide to fire another NEA, which finally allowed the pin to fully shift and the antenna to fully deploy and lock into place.

Assuming no further issues occur during Juice’s long trip through the Solar System, Juice is expected to arrive at Jupiter after four gravity assists in July of 2031. There it will perform multiple science missions until a planned deorbit on Ganymede by late 2035.

See Satellites In Broad Daylight With This Sky-Mapping Dish Antenna

March 31, 2023 by Dan Maloney 16 Comments

If you look up at the night sky in a dark enough place, with enough patience you’re almost sure to see a satellite cross the sky. It’s pretty cool to think you’re watching light reflect off a hunk of metal zipping around the Earth fast enough to never hit it. Unfortunately, it doesn’t work during the daylight hours, and you really only get to see satellites in low orbits.

Thankfully, there’s a trick that allows you to see satellites any time of day, even the ones in geosynchronous orbits — you just need to look using microwaves. That’s what [Gabe] at [saveitforparts] did with a repurposed portable satellite dish, the kind that people who really don’t like being without their satellite TV programming when they’re away from home buy and quickly sell when they realize that toting a satellite dish around is both expensive and embarrassing. They can be had for a song, and contain pretty much everything needed for satellite comms in one package: a small dish on a motorized altazimuth mount, a low-noise block amplifier (LNB), and a single-board computer that exposes a Linux shell.

After figuring out how to command the dish to specific coordinates and read the signal strength of the received transponder signals, [Gabe] was able to cobble together a Python program to automate the task. The data from these sweeps of the sky resulted in heat maps that showed a clear arc of geosynchronous satellites across the southern sky. It’s quite similar to something that [Justin] from Thought Emporium did a while back, albeit in a much more compact and portable package. The video below has full details.

[Gabe] also tried turning the dish away from the satellites and seeing what his house looks like bathed in microwaves reflected from the satellite constellation, which worked surprisingly well — well enough that we’ll be trawling the secondary market for one of these dishes; they look like a ton of fun.

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One Method For Removing Future Space Junk

March 22, 2023 by Bryan Cockfield 18 Comments

When sending satellites into space, the idea is to place them into as stable an orbit as possible in order to maximize both the time the satellite is useful and the economics of sending it there in the first place. This tends to become rather untenable as the amount of space junk continues to pile up for all but the lowest of orbits, but a team at Brown University recently tested a satellite that might help solve this problem, at least for future satellite deployments.

The main test of this satellite was its drag sail, which increases its atmospheric drag significantly and reduces its spaceflight time to around five years. This might make it seem like a problem from an economics standpoint, as it’s quite expensive to build satellites and launch them into space, but this satellite solves these problems by being both extremely small to minimize launch costs, and also by being built out of off-the-shelf components not typically rated for spaceflight. For example, it gets its power solely from AA batteries and uses an Arduino for its operation and other research.

The satellite is currently in orbit, and has already descended from an altitude of 520 km to 470 km. While it won’t help reduce the existing amount of debris in orbit, the research team hopes to demonstrate that small satellites can be affordable and economically feasible without further contributing to the growing problem of space junk. If you’re looking to launch your own CubeSat one day, take a look at this primer which goes over most of the basics.

Hunting For Space Pirates

February 24, 2023 by Bryan Cockfield 14 Comments

Ever since the first artificial satellite was launched into orbit, radio operators around the world have been tuning in to their space-based transmissions. Sputnik 1 only sent back pulses of radio waves, but in the decades to follow ever more advanced radio satellites were put into service that could support two-way communications from Earth to space and back again.

Some of these early satellites were somewhat lacking in security, though, and have been re-purposed by various pirates around the world for their own ends. [Gabe] aka [saveitforparts] is here to show us how to hunt for those pirates and listen in on their radio traffic.

Pirates on these satellites have typically used them for illicit activities, and it is still illegal to use them for non-governmental or non-military purposes, so [Gabe] notes that he will only be receiving, not transmitting. The signals he is tuning in to are VHF transmissions, specifically around 220 MHz. That puts them easily within the reach of the RTL-SDR and common ham radio equipment, but since they are coming from space a more directional antenna is needed. [Gabe] quickly builds a Yagi antenna from scrap, tuned specifically to 255 MHz, and mounts it to an old remote-controlled security camera mount which allows him to point it exactly at the satellite and monitor transmissions.

From there he is able to pick up what looks like a few encrypted and/or digital transmissions, plus analog transmissions of likely pirates speaking a language he guesses to be Portuguese. He also hears what he thinks is a foreign TV broadcast, but oddly enough turns out to be NPR. These aren’t the only signals in space to tune to, either. There are plenty of purpose-built ham radio satellites available for any licensed person to use, and we’ve also seen this other RTL-SDR configured to snoop on Starlink signals.

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