Hi Mark,

thanks for the information.

Can you please explain what this means:

“MESAT1 carries a second radio, an EyeStar transmitter, originally intended to interface with the satellite’s built-in GPS and the GlobalStar network to provide the ground team with accurate, hourly position information.

This aspect of the mission was altered during MESAT1 construction. The EyeStar unit will serve only a minimal function on MESAT1.”

Thanks and regards

Matthias

www.dd1us.dehttp://www.dd1us.de

Von: Mark L. Hammond via AMSAT-BB amsat-bb@amsat.org Gesendet: Sonntag, 15. September 2024 04:53 An: Jon vu2jo0@gmail.com Cc: graham@shirville.com; amsat-bb amsat-bb@amsat.org Betreff: [AMSAT-BB] Re: AO-73 question

Hello, Jon.

We've been helping the MESAT1 team at Univ. of Maine. https://www.mainesat.org/mesat1/

GPS on this LEO satellite does indeed work. The idea of using it for frequency stability is neat :)

You can read https://iaru.amsat-uk.org/finished_detail.php?serialnum=822 and see this: "The MESAT1 spacecraft will also carry an L-band GlobalStar transmitter with a carrier frequency of 1616.25 MHz. This will be used along with the onboard GPS receiver, to provide back to our team, early mission TLEs"

73!

Mark L. Hammond [N8MH] AMSAT Director and Command Station

On Sat, Sep 14, 2024 at 8:13 PM Jon via AMSAT-BB <amsat-bb@amsat.orgmailto:amsat-bb@amsat.org> wrote: Being in LEO orbits, can current day satellites use GPS disciplined oscillator (GPSDO)? They are still below the GEO orbit and should technically be able to receive GPS signals, but for the fact that they are moving very fast. Asking just out of curiosity.

73 de Jon, VU2JO

On Sat, Sep 14, 2024 at 10:30 PM graham shirville via AMSAT-BB <amsat-bb@amsat.orgmailto:amsat-bb@amsat.org> wrote: Hi John,

I am not sure if you have received any other answer but…

AO73 has been operating in full time 24/7 transponder on mode for some time now.

The telemetry is also transmitted at low power at the same time on the nominal 145.935 MHz.

The nominal transponder frequencies remain unchanged: Uplink: 435.150 – 435.130 MHz LSB (Inverting) Downlink: 145.950 – 145.970 MHz USB

But these do drift a for Hz depending upon the on board temperature – back in the day, perhaps twelve years ago, the design of the oscillators was a compromise between stability and power consumption.

JO97, being a more recent design, does not have this “feature”.

73

Graham G3VZV

From: JOHN GEIGER via AMSAT-BB <amsat-bb@amsat.orgmailto:amsat-bb@amsat.org> Sent: Friday, September 13, 2024 7:02 PM To: amsat-bb <amsat-bb@amsat.orgmailto:amsat-bb@amsat.org> Subject: [AMSAT-BB] AO-73 question

Great to see that AO-73 has been QRV again. I seem to remember seeing somewhere that it has shifted frequency somewhat from the published frequencies. Is this correct? What are the current uplink and downlink passbands for it?

73 John AF5CC

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