Category: Applications

MEMESat-1: A Meme-Beaming Cubesat Currently In Development

The Mission for Education and Multimedia Engagement Satellite (MEMESat-1) is planned to be the first meme broadcasting cube satellite ever created. If you aren't down with modern slang and are not familiar with the word "meme", that may be because although first coined in 1976, the modern definition was only added to the Webster-Miriam dictionary in 2015. In the traditional sense a meme is a cultural idea, behavior, style that people can't help but want to share because of how funny/amusing/interesting it is.

But in particular MEMESat-1 wants to broadcast from space the new type of meme definition, which is essentially funny or amusing images/GIFs that internet users and especially youth like to modify and share online through social media. Memes have become a major part of internet youth culture, so this could be an excellent way to speak the language of the next generation and get them interested in space, satellites, amateur radio and building satellite ground stations.

At the moment, the team hopes to launch the satellite by late 2021, and no later than Spring 2022. The satellite will be a cubesat with flash memory containing thousands of meme images that will be broadcast to Earth via a transmitter operating in the UHF 70cm radio band. Enthusiasts on the ground will be able to receive the meme images with a Yagi antenna and we anticipate that RTL-SDRs will be a commonly used receiver. The satellite will also contain an FM UHF/VHF repeater operating in the amateur radio band for ham radio use.

MEMESAT-1 is being developed by letsgo2space.com, a non-profit trying to increase the exposure kids have to STEM topics. Over on Reddit, the founder explains his story and mission:

I went out and started a nonprofit organization, built a website, developed a meme-related anxiety disorder, and am now building a meme-beaming satellite with a group of undergrads at UGA and some industry sponsors. And it’s all for the sake of making a novel meme. We are now fundraising to launch MEMESat-1.

For those who are interested in reading about the trials and tribulations of a 22 year old man-child trying to send memes into space, I’ve included the longer story below.

For my whole university career, I was in search of different work opportunities and internships to see what felt the most fulfilling and to get some of those sweet sweet resume lines. I’ve interned at a plastic factory, the Air Force Research Labs, NASA JPL, and Ball Aerospace. They were all great places filled with awesome people and cool work, but I didn’t feel connected with my work in a way that fulfilled me. So, for the past 3 years me and my buddies have been joking around about building a satellite that beams down memes from space.

Enter MEMESat-1.

While I was working at JPL, me and some buddies got together to toy around with space start-up ideas. We joked more about MEMESat, and bought the memesat.com domain back in 2018. Due to timing and other life events the start-up idea kind of fell off. One of my pals is pursuing his Ph.D, and the other is working as a spacecraft engineer full-time. I on the other hand, still had 2.5 years of school left.

Work on the MEMESat concept slowly came to a halt by the end of 2018, but picked up again in Spring 2019 when I came up with the acronym the Mission for Education and Multimedia Engagement Satellite (MEMESat-1). I kept telling my classmates and friends about the project idea as a joke, but they thought I was being serious and told me to go for it. By May 2019 I had worked out a deal with some universities to use their space, and began building the website. Over that summer, my job left me some spare time, so I started ramping up the social media for MEMESat-1 by posting daily spacefacts to instagram. I also worked on some preliminary design studies to see if the mission would be feasible, and decided that it definitely was. I also spent the summer researching how to form a company, and what the best company structure would be.

In August 2019, I returned to school and began to work on forming a company. Some great profs at GT gave me the advice to start a nonprofit, so I searched for some pro bono legal advice on starting a nonprofit. I took some of the lawyer’s advice and found some willing Directors for the company, and filed to form a nonprofit corporation - called Let’s Go to Space, Inc.

Around that time, I posted to reddit and got a bunch of attention from you guys, so I figured I should work my hardest to make it happen. I spent months emailing every space related company I could find or even think of. I have much more respect now for people that lead telemarketing campaigns, because it is really hard to convince random people over the phone/email to give you large sums of money. Now, I am happily partnered with Ball Aerospace and sponsored by Blue Canyon Technologies. I’m also in talks with some launch providers about a free launch and some help launching my lesson plans/experiment kits to classrooms all over!

We have passed the point of no return and have nowhere to go but upwards. My parents are confused and slightly disappointed that their rocket scientist son has given up any sort of salary in an effort to appease his ‘internet friends’. God bless you magnificent weirdos for keeping me going. Ad Astra Per Memes.

Currently letsgo2space is fundraising and looking for $30,000 to fund the launch of MEMESAT-1. You can either donate any amount or submit a meme for their broadcast database for $1.69 via their website.

MEMESat-1 Logo
MEMESat-1 Logo

Creating a Low Cost Ground Penetrating Radar with Two HackRFs

A ground penetrating radar (GPR) is a system that uses RF pulses between 10 to 2.6 GHz to image up to a few meters below the ground. A typical GPR system consists of a transmitting radio and antenna that generates the radar pulse aimed towards the ground, and a receiving radio that receives the reflected pulse.

GPR is typically used for detecting buried objects, determining transitions in ground material and detecting voids and cracks. For example, in construction it can be used to determine rebar locations in concrete, and in the military it can be used to detect non-metallic landmines and hidden underground areas. 

These GPR devices are usually very expensive, however researchers Jacek JENDO & Mateusz PASTERNAK from the Faculty of Electronics, Military University of Technology, Poland have released a paper detailing how two low cost HackRF software defined radios can be used to create a simple GPR.

Their system uses a step-frequency continuous waveform (SFCW) signal which scans over multiple frequencies over time, and  the software was written in GNU Radio. In their tests they were able to detect a dry block of sand buried 6 cm below the ground, and a wet block 20 cm below. 

Ground Penetrating Radar with two HackRF software defined radios.
Ground Penetrating Radar with two HackRF software defined radios.

Look4Sat: An Android App for Tracking and Predicting Amateur Radio and Weather Satellite Passes

Thank you to Arty Bishop for submitting news about his recently released Android App called Look4Sat. Look4Sat is a satellite tracker and pass predictor with a focus on amateur radio and weather satellites. The app is free, ad free, and open source on GitHub.  Arty writes that he's programmed this as a learning exercise and notes:

I always wanted to have an offline and not bloated satellite tracker on my phone, as carrying the laptop at all times is kinda not too handy.

The app uses predict4java library under the hood and is written in Kotlin. The TLE files are from Celestrak and the transmitters info is from SatNOGS and once they are  ownloaded the app doesn't need an internet connection.

The app creation and design is hugely inspired by Gpredict which is an absolutely brilliant piece of software. Thank you, Alexandru!

Obviously there is no ads and it's totally free. Hope more people find Look4Sat useful.

The features include:

  • Calculating satellite passes for up to one week (168 hours)
  • Calculating passes for the current or manually entered location
  • Showing the list of currently active and upcoming satellite passes
  • Showing the active pass progress, polar trajectory and transceivers info
  • Showing the satellite positional data, footprint and ground track on a map
  • Offline first: pass prediction is done offline. It's up to you to decide when
    to update the TLE file and the transceivers DB. (Updates once a week are recommended)
Look4Sat Android App Screenshots
Look4Sat Android App Screenshots

Shazam Style Automatic Signal Identification via the Sigidwiki Database

Thank you to José Carlos Rueda for submitting news about his work on converting a "Shazam"-like Python program made originally for song identification into a program that can be used to automatically identify radio signals based on their demodulated audio sounds. Shazam is a popular app for smartphones that can pull up the name of any song playing within seconds via the microphone. It works by using audio fingerprinting algorithms and a database of stored song fingerprints.

Using similar algorithm to Shazam, programmer Joseph Balikuddembe created an open source program called "audio_recogition_system" [sic] which was designed for creating your own audio fingerprint databases out of any mp3 files.

José then had the clever idea to take the database of signal sounds from sigidwiki.com, and create an identification database of signal sounds for audio_recogition_system. He writes that from his database the program can now identify up to 350 known signals from the sigidwiki database. His page contains the installation instructions and a link to download his premade database. The software can identify via audio that is input from the PC microphone/virtual audio cable or from a file.

Fingerprinted Audio Samples of Radio Signals
Fingerprinted Audio Samples of Radio Signals

A FM Radio Passive Radar System from Two RTL-SDR Dongles

Over on his blog, Max Manning has posted about his senior year design project which was an RTL-SDR based passive radar system that he created with his project partner Derek Capone. Max's writeup explains what passive radar is, and how the theory works in a very easy to understand way, utilizing graphs and short animations to help with the understanding. The rest of the post then goes into some deeper math, which is also fully explained.

Passive Radar works by using already existing powerful transmitters such as those for TV/FM. A receiver listens for these signals being reflected off of objects like aircraft and vehicles, and compares the reflection with a signal received directly from the transmitter. From this information a speed/range graph of detected objects can be calculated

For hardware, the team used two RTL-SDR dongles with the local oscillators connected together. A standard dipole is used as the reference antenna, and a 5-element Yagi is used as the surveillance antenna.

Max's post is a great read for those trying to understand how to do passive radar with a KerberosSDR which is our 4x coherent input RTL-SDR unit available from the Othernet store or Hacker warehouse. Being a radio capable of coherency, it is useful for applications like passive radar and direction finding. 

Their code is all open source and available on GitHub. We note that their code should also work with KerberosSDR with only either zero to minor modifications required. However, for the KerberosSDR we also have our own passive radar code available which might be a little easier to setup via the GUI.

Passive Radar with Two RTL-SDR dongles sharing a single clock.
Passive Radar with Two RTL-SDR dongles sharing a single clock.

Decoding NavTex with an SDRplay RSPDx, SDRUno and YanD

Over on YouTube TechMinds has uploaded a new video explaining NavTex and showing how to decode it with an HF capable SDR like the SDRplay RSPDx. NavTex is a marine digital data radio service designed for transmitting information like navigational and meteorological warnings, weather forecasts and maritime safety information. It is broadcast in either the MW frequency band at 490 kHz and 518 kHz or in the HF band at 4209.5 kHz.

In the video TechMinds uses a guide put out by Mike Ladd from SDRplay (pdf warning). The guide explains how to connect SDRuno to a NavTex decoder called YanD via a virtual audio cable. The rest of the video shows a NavTex message being decoded, some sample messages, and a closer look at YanD. 

Even if you don't use an SDRplay, the guide could be adapted for other SDRs too.

Decoding NavTex with Software Defined Radio - SDRuno RSPdx

A Hydrogen Line Telescope Made from Cereal Boxes and an RTL-SDR

SpaceAustralia.com have recently been hosting a community science project that involves encouraging teams to build backyard radio telescopes that can detect the arms of our Milky Way Galaxy by receiving the Hydrogen line frequency of 1420 MHz.

This can be achieved at home by building a horn antenna out of cardboard and aluminum foil, and a feed from a tin can. Then the Hydrogen line and galactic plane can be detected by using an RTL-SDR, LNA, and software capable of averaging an FFT spectrum over a long period of time.

While most horn antennas are typically made from four walls, one participant, Vanessa Chapman, has shown that even trash can be used to observe the galaxy. Vanessa's horn antenna is made from multiple cereal boxes lined with aluminum foil and an old tin fuel can. The boxes are held together by some string and propped up by some sticks.

With her cereal box horn antenna combined with an RTL-SDR Blog V3, and an RTL-SDR Blog Wideband LNA, Vanessa was able to use software to average the spectrum over time as the galactic plane passed overhead, revealing the Hydrogen line peak and corresponding doppler shift from the galactic plane.

Vanessa's Hydrogen Line Radio Telescope made from Cereal Boxes
Vanessa's Hydrogen Line Radio Telescope made from Cereal Boxes

If you don't know what the Hydrogen line is, we'll explain it here. Hydrogen atoms randomly emit photons at a wavelength of 21cm (1420.4058 MHz). Normally a single hydrogen atom will only very rarely emit a photon, but space and the galaxy is filled with many hydrogen atoms so the average effect is an observable RF power spike at 1420.4058 MHz. By pointing a radio telescope at the night sky and integrating/averaging the RF power over time, a power spike indicating the hydrogen line can be observed in a frequency spectrum plot. This can be used for some interesting experiments, for example you could measure the size and shape of our galaxy. Thicker areas of the galaxy will have more hydrogen and thus a larger spike, whereas the spike will be significantly smaller when not pointing within the galactic plane. You can also measure the rotational speed of our galaxy by noting the frequency doppler shift.

KerberosSDR 4-Channel RTL-SDR Passive Radar with Peak Hold Display

Recently we've been testing a simple peak hold for the KerberosSDR passive radar display. This results in some nice graphs that show aircraft and vehicle activity over time. 

Passive radar works by using already existing transmitters such as those for HDTV and listening for reflections that bounce off of RF reflective objects. With a two antenna setup, it is possible to generate a bistatic range/doppler speed graph of reflected objects.

With the reference Yagi antenna pointed towards a 600 MHz DVB-T tower, and the surveillance antenna pointed to an airport we were able to obtain the graph below. The top two large traces show aircraft heading towards our station, whereas the bottom traces show aircraft leaving the airport. Also visible are multiple blips with smaller doppler speeds, and these correspond to vehicles.

KerberosSDR Passive Radar Display Peak Hold
KerberosSDR Passive Radar Display Peak Hold

The code on the KerberosSDR git will be updated in a few days time. We are also working on a more comprehensive passive radar tutorial that will try to explain concepts like processing gain, bistatic ranges and other important tips for getting good passive radar results. At the same time we're also working on improving direction finding ease of use by prototyping antenna switches for calibration, and working on getting 4-channel beamformed passive radar working which will allow us to plot passive radar returns on a real map.

The KerberosSDR is our 4-channel phase coherent capable RTL-SDR unit that we previously crowdfunded back in 2018.  With a 4-channel phase coherent RTL-SDR interesting applications like radio direction finding, passive radar and beam forming become possible. It can also be used as 4 separate RTL-SDRs for multichannel monitoring. KerberosSDR is currently available from the Othernet store and Hacker Warehouse for US$149.95.