Launch day - signals logged here at the 'Zarya' location in the UK at 2247.5 MHz. A vague report from another location leads to the conclusion that 2272.5 MHz might also be in use. Transmissions then detected at 2247.5 MHz and 2272.5 MHz by Greg Roberts in South Africa.

Sven Grahn reports that, when communicating with a ground station, the satellites are using the standard SGLS technique of locking the transmitter frequency to the received frequency of the uplink. While over Europe, the satellites are communicating via the Oakhanger ground station in the UK.

Visual observation by Greg Roberts of South Africa agrees with the radio-derived separation measurements.

Analysis of observations to date confirms that the two satellites are separating at the rate of 42s per day in time - about 2.2 degrees per day when measured along the orbital arc. There appears to have been no change in the orbit of either since launch.

Radio observations show the separation rate to have reduced. The rate had been consistent at 42s per day since launch. Tracking back the new separation observations indicates that an orbit adjustment was made by SV2 (2009-052B/35938), the leading satellite, late on Oct 7.

Strong transmissions received in the UK from SV2, the leader of the pair, several times during the early part of the day. SV1's transmitter was relatively weak but the indication is that it is still in its initial orbit. The new separation rate is measured as 22s per day.

Separation rate measures as 21s per day (+/-4s), about fifty percent of the earlier value. This is equivalent to about 1.1 degrees per day.

There is still no indication of any orbit adjustment by SV1 but it looks as thought the manoeuvre by SV2 on Oct 7 was followed by a small 'trimming' manoeuvre twenty four hours later in order to slow the separation rate a fraction more.

Today's measurements indicate that a minor orbital adjustment on Oct 11 increased the separation rate to 23s per day. Without further adjustment, operational separation will now be reached late Oct 14 UTC (see Oct 15 entry).

Previous measurements of separation did not take account of the Earth's rotation between passes of SV1 and SV2. It became apparent when comparing the plot with figures computed by Ted Molczan. Points on the plot have been corrected, and the revised estimate for reaching operational separation is during the morning of Oct 16 UTC.

Observations from the UK while the pair of STSS Demonstrators was providing usable passes (up to 09:30 UTC) showed no signs of either satellite having manoeuvred. However, relative measurements of their times of Closest Approach showed that the critical separation of 35 degrees was reached at about that time. Hopefully, observations on Oct 17 will show that one of the satellites has adjusted its orbit.

The separation had exceeded 35 degrees by the time the satellite pair was making passes across the UK during the early morning.

Without any indication of an orbit adjustment by either satellite, the separation continues to increase at a steady rate.

Vacation break has interfered with observations - but the gap will be filled over the next few days as some automatically-collected data is analysed. An observation late Oct 31 indicates that the separation of the two satellites is about 51 degrees of orbital arc and still increasing, possibly to assist tests of the two satellites' linked systems. The separation rate is very close 1.0 degrees per day.

Still separating .... and "Hi" to site vistors from Northrop Grumman and Aerospace Corp!

No measurements were possible on the late Oct 8 passes because of a breakdown in a radio receiver power supply. However, it now back up and running.

Late Nov 10, the separation was still increasing steadily. In 4-5 days time, the satellites will lose visibility of each other. If the separation continues to increase after that they will start to lose mutual visibility of airspace above the Earth so stereo viewing will not be possible.

The signal strength of transmissions from SV1 (the follower) is distinctly lower that that from SV2 but the transmitter is responding to commands. The question is starting to form of "is there a problem?".

Yesterday's question is answered. SV2 has raised its orbit so the two are no longer separating. The separation reached a maximum of about 63 degrees measured as the central angle of the orbit and may now be reducing. Another observation or two is needed to confirm this. So far all significant orbit adjustments have been done by SV2. The maximum separation reached was such that each satellite appeared to be very low on the other's horizon, probably to test the satellites' linked systems at extreme range.

Measurement around 20:00 UTC today indicates that the two satellite smay station keeping with a separation of about 63 degrees measured at the centre of the Earth. This situation was reached sometime November 11. The received strength of SV1's transmission has returned to the same level as SV2 and both are coming through strongly.

Today's observations indicate that a slow drift back towards each other has started - the previously reported "station keeping" was incorrect. The pass here of SV2 around 22:20 UTC exhibited a distinct change in the transmission frequency since the previous day, measuring 2272.513 MHz against the established norm of between 2272.517 and 2272.519 MHz.

It seems the two may now be station keeping with a separation of just under 62 degrees measured round the orbit arc. The downward slope may be a result of the error bounds in individual observations.

Transmission frequency of SV2 continues at 2272.513 MHz. There is a pattern of frequency variations in both satellites (more to follow on this).

For about two minutes around 23:27 UTC, SV2 seemed to lock-on to a ground station and the frequency stepped down noticeable before steppng back up to a continuation of the already-established Doppler curve. If it was indeed a ground station lock then the location was somewhere to the west of the UK rather than the usual nearby one - maybe Greenland?. See "Frequency Lock Special Case" in the STSS Tracking pages.

Now that a few days observations are available since the orbit adjustment, it can be seen that the satellites are closing on each other at the rate of about one third of a degree per day measured as an arc around the orbit.

On three passes this evening, SV2 was approx 5s late so its orbit has been raised and the closing rate has accelerated a little.

The note from Nov 20 suggesting an orbit change was more in hope than reality as today's observations show SV2 to be running pretty well on time - so no significant manoeuvre!

No change - still closing at 0.3-0.4 deg per day with the separation angle currently 57 degrees of orbit arc. If nothing changes it will be late-January before the expected 35 degrees central separation is reached.

It remains to see if this is significant but most of today's passes by SV2 involved the satellite's receiver being locked on to the uplink. It suggests heavy data traffic and a 'meaningful conversation' with the ground.

After these first few weeks, sufficient measurements of transmission frequencies have been gathered to draw some conclusions. See "Frequencies & Variations" in the STSS Tracking pages.

Looking at the plot showing the separation, the manoeuvre around Nov 12 is not clear cut. A revisit of the observations reveals a calculation error that affects two of the readings. Allowing for it makes it much more clear in that the orbit adjustment by SV2 occurred late in the day on Nov 11.

Interesting event during a pass here of SV1 at round 12:20 UTC: the signal was very weak and there was a problem locking to the local uplink, though there is no way of knowing which end had the problem. At one point, it was locking/unlocking so rapidly that the screen trace gave the impression of it transmitting in both modes simultaneously.

On the 16:50 UTC pass, STSS Demo SV1 repeated its lock/unlock 'hopping' from the previous day. All the earlier passes, the transmitter had been free running at 2247.499 MHz. During the course of the day, SV2 exhibited its usual mixture of locked and unlocked behaviour with no obvious issues.

Good passes from both vehicles today and both exhibited free-running and locked behaviour. No sign of the lock/unlock issues witrh SV1 - the pass seemed fine.

There looks to have been a very small change in the orbit of SV2 around Dec 7, small enough for it be the result of attitude control thruster firings.

Everything about normal - a single'locked' transit from each sateliite - but then.... it's Saturday!

Both satellites have exhibited a drop in transmission frequency today, something usually associated with an increase in power reserves. It could be a blip or maybe it's preparation for the Christmas break and onboard activity is being wound down for a few days. See "Frequencies and Variations" in the left hand menu.

More problems with SV-1's frequency lock today.

Most of the SV1 passes today had transmissions locked to the uplink - maybe trying to diagnose/resolve the unlocking problem from earlier days?

2009 Dec 23, the transmission frequency of SV2 returned to it's immediate post-launch value of 2272.508 MHz . It has remained steadily at that value ever since - see "Frequencies and Variations".

If the target separation for the satellite pair is 35 degrees of central orbit angle as outlined in the Aerospace Corp document, then the required separation will be reached 2010 Feb 1 (+/- 1 day).

At 00:00 UTC today, the separation was 45 degrees and the rate of closing measured at 0.34 degrees per day. Obviously, a manoeuvre by one of the satellites has the potential to change the date.

SV1 still showing signs of being unable to maintain a lock to the uplink.

After eighteen days of the frequency being very stable, SV2 has now jumped +4 kHz.

The transmission frequencies of both STSS Demo SV1 and SV2 started to rise at the end of the first week in January, suggesting they may be 'waking up' after the Christmas break in mission control.

Both transmitters weaker than recently. SV1 shows signs of failing to lock to the uplink.

Both transmitters now running quite strongly again.

Today's morning measurement of separation indicates that SV2 made an orbit adjustment overnight 2010 Jan 27/28 (around 03:00 UTC) and is now station-keeping with SV1. The separation is 36 degrees of orbital angle (+/-1 degree).

Radio observations later in the day when the STSS satellites came back into view from the UK around 23:30 UTC confirm the manoeuvre, the separation and the station-keeping.

Refined data - manoeuvre seems to have been in the early hours of Jan 28 UTC. Within observational error bounds (+/-2s), the separation seems to be constant but any small drift will not show for several days from the radio observations.

The current estimate for the separation is 36.25 degrees (+/-0.25) which explains why the manoeuvre came a little earlier than anticipated. It was not expected to happen for another four days when the separation would have been 35 degrees.

All manoeuvres to date have been undertaken by SV2.

The STSS Demonstrator satellites seem to be settled in their operational orbital configuration so no further updates to the plots will be published.