Receiving radio signals from polar orbiting weather satellites

In my last blog post I wrote ...

It's easier than ever to track National Oceanic and Atmospheric Administration (NOAA) polar orbiting weather satellites, ... Source Credit: Tracking polar orbiting weather satellites.

I used the n2yo.com Web site to get 10-day predictions for NOAA 18. I noticed a good pass on Tuesday, 05 September 2023 so I grabbed my Baofeng UV-5R radio and went outside to a clear place in order to listen for the satellite signal. I was delighted to hear the distinctive sound of the APT radio signal soon after I set up my "ground station."

Recording

I recorded the satellite pass by simply holding the Baofeng UV-5R radio speaker close to the internal microphones on my Apple iPad mini 6 -- a technique demonstrated in a YouTube video by "saveitforparts." I used the Shure "MOTIV Audio" app (for iOS) to record the pass as a 16-bit 44.1 kHz WAV file (mono).

The duration for the pass was 15 minutes. [Start: 12:08. Max: 12:16 (81 degrees, W). End: 12:23.]

First minute of the pass.

One minute centered around the midpoint of the pass.

More noise is to be expected at the beginning and ending of a weather satellite pass, when the spacecraft is near the horizon. The signal should be stronger and clearer when the satellite is nearly overhead, but as you can hear in the preceding WAV file there's still too much noise for a good image.

Decoding

It's easier than ever to decode weather satellite signals to create images. In this case I used "open-weather apt," the free online weather satellite image decoder.

"open-weather apt" seems to work well but only works with 16-bit 11,025 kHz WAV files, so I had to resample the 44.1 kHz WAV files I recorded using my iPad. I used a free audio editor called "Audacity." There are many "how to" videos on YouTube such as this one by Chris Murphy.

Here is my first attempt at direct reception of an APT radio signal.

05 September 2023 | NOAA 18

Not exactly perfect, but hey, experts say it's not bad for my first pass.

Tech tips for decoding using "open-weather apt"

The "open-weather apt" page includes a link to a sample WAV file that you can use to hear and see what a good pass is like.

Download the sample file and listen to it using an application such as QuickTime Player (for Apple and Windows). You can hear both the beeping and "metronome" sounds much more clearly than in my recording.

Then upload the WAV file in order to familiarize yourself with the decoding process. Here's one iteration of the decoded image.

The preceding composite image shows both the visible (left) and infrared (right) channels for the sample satellite pass. Just a little better than mine!

What are the take-aways?

It's easier than ever to receive APT radio signals from weather satellites, with one critical caveat: It's as challenging as ever to receive a strong, clear signal.

• It's clear (pun intended) I need a better antenna than the small "rubber ducky" antenna that comes with the Baofeng UV-5R. I'm considering upgrading to a "V dipole" antenna.
• Signal reception seemed to be better with the "rubber ducky" antenna oriented horizontally (parallel to the concrete pavement), rather than vertically as recommended by YouTuber "saveitforparts." This was especially true when the satellite was nearly overhead -- the dropout might be related to the "null" of vertical antennae.
• I setup my "ground station" on the top of a seven story parking garage located in exurban Washington, D.C. There was too much ambient noise for a clean recording by simply holding the radio speaker close to the microphones in my iPad mini 6, as suggested by YouTuber "saveitforparts."

Perhaps the biggest take-away is a good question. Why try to receive weather satellite images directly when so much high quality imagery is available on the Internet for free? I can't answer that question for you, but I can say for me the challenge is to see whether relatively inexpensive gear can be used to get reasonably good results. Although the quality of my first weather satellite image is disappointing, I was able to successfully track NOAA 18 and hear a radio signal from the satellite -- accomplishments that I can and will build upon.

Related Resource: APT and HRPT

There are two types of NOAA polar orbiting weather satellite imagery that amateur radio enthusiasts attempt to receive.

Direct Readout Services include the Automatic Picture Transmission (APT) for low resolution imagery and High Resolution Picture Transmission (HRPT) for higher-resolution imagery. Source Credit: NOAA Satellite Information Service, U.S. Department of Commerce.

Direct reception of HRPT radio signals is way beyond my level of expertise.

Copyright © 2023 Walter Sanford. All rights reserved.

Tracking polar orbiting weather satellites

It's easier than ever to track National Oceanic and Atmospheric Administration (NOAA) polar orbiting weather satellites, receive signals from those satellites, and decode the signals to create an image showing the Earth from space at the time of a given satellite pass.

Let's begin with a quick overview of how to track NOAA polar orbiting weather satellites.

n2yo.com | Track 3 satellites

Currently there are three operational environmental satellites, including NOAA 15, NOAA 18, and NOAA 19. Go to the n2yo.com Web site in order to track these satellites (and more).

By default, the track of the International Space Station (ISS) is displayed on a world map. To track one of the NOAA weather satellites, move your mouse cursor over the tab labeled "Most tracked" in the blue menu bar at the top of the screen; select one of the NOAA polar orbiting weather satellites, e.g., NOAA 18. Click on the hyperlinked text labeled "10-day predictions." The next screen shows a table of passes for NOAA 18 for the next 10 days. Click on "All passes" rather than "Visible passes" (the same button toggles from one setting to the other). Times shown in the table are local times.

Excerpt from NOAA 18 10-day predictions.

Look for a pass when the elevation (El) is close to 90 degrees. Then grab your radio and go outside to a clear place. Tune the radio to the satellite frequency, in this case 137.9125 MHz for NOAA 18, and listen for the satellite during the window of time between the "Start" and "End" times shown in the table.

Wait, what radio? Oh yeah, you will need a radio to receive signals from the NOAA polar orbiting weather satellites. That's the bad news. The good news is a relatively inexpensive radio such as the Baofeng UV-R5 should work just fine. The radio sells on Amazon for around $20. Stay tuned for more information about this step in my next blog post.

In the meantime, try tracking and observing the International Space Station. It's easy to spot the station at night during a nearly overhead pass.

Copyright © 2023 Walter Sanford. All rights reserved.

Vagablog revival!

 After years of dormancy, "Vagablog" is about to roar back to life! I will almost certainly change the name of the blog to reflect my new interests, although I don't plan to delete the old content -- believe it or not, some of it is still useful.

Stay tuned for more information in the next few days.

Independence Day

With no disrespect intended toward the United States of America, I celebrate my personal “Independence Day” today: 01 July 2011 is the two-year anniversary of my retirement from Fairfax County Public Schools. Thank God I'm alive to enjoy my freedom!

Project Noah versus Leafsnap

Project Noah and Leafsnap: Two free apps for exploring the natural world; two different solutions for field identification of fauna and flora. One app works amazingly well; the other app works, but not as well. A list of pluses and minuses for both apps follows, along with a summary of the results of my field testing and a recommendation for educators.

Project Noah
(+) Visually appealing user interface (UI) – In a word, yes.
(+) Built-in camera – My Noah/New Spotting/”Take new photo” (plus access to iPhone “Camera Roll”)
(-) Built-in field guide – The Project Noah Field Guide is not a field guide in the traditional sense of the word, rather it is more like a crowdsourced field guide. Photos and related narrative text are submitted by Project Noah “citizen scientists”: Nomenclature and content quality varies widely throughout the field guide; some groups of animals and plants are either underrepresented or not represented.
(-) Feedback – "Help me ID this species." I tapped "YES"; no feedback (since 23 May 2011).
(+/-) Geo-referenced data – Optional map view available (see example); photos saved to “Camera Roll” are not geotagged (see example).
(+/-) Option to participate in actual scientific research projects – “My Missions.” Your field observations may never be used by real scientists unless you opt to participate in one or more missions.
(+) Performance incentives – “My Patches,” like virtual scouting merit badges
(-/+) Built-in documentation and Web support – No built-in help; better Web pages than Leafsnap.
http://www.projectnoah.org/
(-) Universal app/iPad version – Not available

Leafsnap
(+/-) Visually appealing user interface – Yes. Leafsnap UI somewhat less appealing than Project Noah.
(+) Built-in camera – “Snap It!” (plus access to iPhone “Camera Roll”)
(+) Built-in field guide – Database currently features 2,620 high-resolution images of 185 tree and plant species.
(+) Feedback – Immediate and very reliable. Leafsnap correctly identified 8/9 trees that I tested; the second result was the correct ID for the 9th tree (a fact verified easily by comparison with field guide database).
(+) Option to participate in actual scientific research projects – By design, all field observations are used to build scientific database.
(+/-) Geo-referenced data – Optional map view available (see example); photos saved to “Camera Roll” are not geotagged (see example).
(+) Performance incentives – “Geodialist’s Collection” ("Geodialist" is my Leafsnap username)
(+/-) Built-in documentation and Web support – Tap “i” on any page for more information; poor Web support.
http://leafsnap.com/
(+) Universal app/iPad version – iPad version available (“Snap It!” doesn’t work with iPad 1.)

Summary
Overall, Project Noah has twice as many minuses as Leafsnap, and there are more pluses than minuses for Leafsnap. Most importantly, Leafsnap provides timely, reliable feedback while Project Noah fails to deliver this key success factor consistently.

As a former science teacher, I am conflicted by the thought of using Project Noah with students. I’m a big advocate of hands-on learning (a.k.a., learning by doing) and technology-enriched instruction. But I prefer “guided discovery” over random experimentation, that is, carefully crafted hands-on activities designed to lead students to scientifically accurate conclusions. At best — that is, with guidance from a good teacher — working with Project Noah could be a great experience for students; at worst, it could be an exercise in frustration (see Editor’s Note, shown below). Bottom line: Leafsnap is the only app I recommend for use with students. In my opinion, Project Noah is more appropriate for adults than children.

Related Resources:

• See the enhanced version of this blog post on my Posterous photoblog, enriched with more graphics.
• Field Test: Leafsnap app

Editor's Note: In the interest of fairly evaluating Project Noah, I re-tested the app by adding a "New Spotting" to "My Noah." I tapped "YES" in response to the prompt, "Help me ID this species." This time, I received two "Comments" later the same day, as indicated by the red badge on the "My Noah" page. I tapped "My Spottings": On the "My Spottings" page, I tapped the right arrow on the first "Needs ID" spotting (that displays an icon indicating two comments); on the "Comments" page, two Project Noah participants correctly identified the plant as a Hydrangea macrophylla (Lacecap). Sounds good -- that's the way it's supposed to work, right? A couple of questions arise: 1) What are the qualifications of the commenters? (With no disrespect intended, aren't you naturally a little skeptical of someone who goes by the moniker, "Monkey-mind?") There is no way to either access a commenter’s bio, or communicate directly with a commenter via Project Noah. 2) What if the commenters had misidentified the plant? Not so good, and arguably worse than no feedback. (Remember the teachers’ old saw that says students must work harder/longer to unlearn misconceptions and misinformation? It’s true!) Project Noah's highest priority should be to devise a procedure that provides timely, reliable feedback EVERY TIME a participant requests help; until this objective is achieved, I remain very reluctant to recommend its use by educators.

Easy audio Tweets using Audioboo

Audioboo is a simple tool for microblogging audio clips via Apple iOS and Android mobile devices; a Web interface is also available (Safari Mobile is not supported at this time). For more information, see "Getting Started with Audioboo" and the video, "Intro to Audioboo on Vimeo."

Soon after I got my first Apple iPhone, I downloaded Audioboo app for iOS and created an account. Honestly, I never used Audioboo until after I started using Twitter. I realized recently that Audioboo can be set to automatically cross-post "boos" to other social media services such as Twitter -- a clever work-around that enables me to literally say more than is possible in a 140-character Tweet!

There is a five-minute time limit for "boos" recorded using the free version of Audioboo; there is no time limit for "boos" recorded using Audioboo Pro. The Audioboo Web interface functions like the apps for mobile devices, with the additional feature that users can upload pre-recorded audio files (use the device of your choice to create "boos" that sound polished). A Web Widget can be used to automatically generate the HTML code for a customized embedded "boo" playlist player (similar to the one shown below).

Audioboo app is simple and straightforward -- it works as advertised and works well. I have a few suggestions for improvement:

1. It would be nice to see the app feature some sort of audio editor, even a rudimentary one. As it stands, there are two options for editing a recording: Pause/Resume (append the recording); and/or Delete Draft (a complete do-over). Mobile audio recording doesn't have to be a one take and you're done process, as shown by Audiofile Engineering's FiRe app for iPhone.
2. Add a setting for local time. The time stamp shown on the Flash "boo" player appears to be Universal Time (UTC).
3. And what's up with the Flash "boo" player? Seriously, if there's an Audioboo app for iOS then then the Web player should be completely compatible with Safari Mobile. Can you say HTML5?

My latest "boo" is called "Spring thunderstorm in Alexandria, VA USA," shown below (Flash required). The audio clip was recorded using my iPhone's built-in microphone; as a result, the sound quality is admittedly poor. Audioboo automatically cross-posted the "boo" as a "Tweet" to Twitter.


Audio clip URL: http://audioboo.fm/boos/339761-spring-thunderstorm-in-alexandria-va-usa

Tech Tip: "Boos" are not cross-posted to other social networking services such as Twitter unless you are logged in to your Audioboo account.

Breaking news: TPE on sale this weekend only

The Photographer's Ephemeris app (TPE for iOS) -- one of two noteworthy Apple iOS apps for planning photo shoots of the Sun and Moon -- is on sale for $3.99 this weekend only. That's right, for two days only you can buy TPE for less than the price of LightTrac ($4.99), a similar yet much less robust app. Don't sleep on this extraordinary offer!