Archief voor categorie: Satelliet nieuws

Amateur Satellite NO-44 (aka PCSat) has entered into the wrong mode and is broadcasting APRS packets in FM over the 144.390 weak signal section of the 2m band.Whilst this is a USA / Region-2 APRS frequency, it is not in Region-1/3. The problem has been the topic of a series of investigations/comments has and now been confirmed as NO-44

Bob Bruninga WB4APR is aware and hopefully the amateur satellite community will make a determined collaborative effort on a recovery/reset (or closedown) shortly, despite the challenges this involves

Whilst I wish the effort well, please also consider this as an example of why close liaison should be maintained by Member Societies with all satellite groups/activities (inc university cubesats etc) to ensure correct frequency coordination and band plan alignment does occur in order to avoid further interference incidents and comply with ITU regulations which require full control and closedown facilities (see below)

Best regards
Murray G6JYB

RR 25.11 Administrations authorizing space stations in the amateur-satellite service shall ensure that sufficient Earth command stations are established before launch to insure that any harmful interference caused by emissions from a station in the amateur-satellite service can be terminated immediately. (See No. 22.1).

RR 22.1 Space stations shall be fitted with devices to ensure immediate cessation of their radio emissions by Telecommand, whenever such cessation is required under the provisions of these Regulations.

An FM APRS signal has been received in England causing interference to the MGM frequency and weak-signal Meteor Scatter (MS) operation which is just
below 144.390 MHz. A MS DXpedition was disrupted by such activity earlier in the month and interference has been occurring at various times since.

Bob Bruninga, WB4APR, explains that the beacon was planned over 15 years ago for operation only when PCSAT is over North America based on published band
plans at that time. Now, after 14 years on orbit, the ability to turn that backup beacon off has been lost.

PCSAT (now 14 years old) had a backup fail-safe beacon on 144.390 that would activate after any unknown spacecraft reset to give a backup comm link in
case the primary 145.825 channel died.  Being on the North American APRS frequency with hundreds of IGates there would always be at least one that
would hear this “emergency call home” from PCSAT even though the channel is generally saturated.  It worked.

The problem is, that now PCSAT resets on every orbit due to negative power budget and so, on every orbit that beacon comes back on.  Even if we did get
a command up to reset it, that setting would last only 15 minutes to the next eclipse.

We learned our lesson!  That was our FIRST amateur satellite and we sure learned NOT to use a “connected-packet-command link” that needs ACKS and
Retries and logon passwords  just to LOGON before you can even send a SHUTUP command.  All our satellites since, operate without the multiple Send,
connect, ACK, retry, ACK, command, ACK overhead…. just to get one command understood.  Now, only the receiver on the spacecraft has to be functional
to command it to silence in a single packet.  But too late for PCSAT.

Bob Bruninga