FUNcube-1 – Battery Voltage – Whole Orbit Data

There are presently three FUNcube based missions in orbit – currently all of them have active, linear U/V transponders. The current status of each of these can always be checked on the useful AMSAT-NA status page https://www.amsat.org/status/ and an update on each of them is provided below. Please have FUN using them!

AO73 – FUNcube1. As previously reported AO73 appears to be experiencing some power issues after 8+years in orbit.

The battery is not charging to the same voltage as it did up to early November last year. The spacecraft has experienced many months of continuous sunlight over the past couple of years and this has resulted in high (around +30C) onboard temperatures. This environment may have “cooked” the cells although presently we do not see any direct evidence of this.

We can see that the stable bus voltage indicated at the end of charge is now much lower and depends on the current being taken by the on-board systems. The solar panel currents appear to be similar to those recorded soon after launch. The current best theory is that we are seeing the effect of some increased resistance in the supply circuit between the eps charging circuit and the battery. Although we do not have access to a fully detailed circuit diagram of the EPS we believe that there is an “ideal diode” in this line to prevent discharge of the battery back through the EPS circuitry. We understand that this is actually a MOSFET device and the suspicion is that this may now be showing signs of radiation damage.

So an operational mode has been selected that can be hopefully sustained for some time. From today AO73 is in continuous transponder mode and is available for use 24/7. Low power telemetry is also being transmitted and reports of the data are very welcome via the FUNcube Data Warehouse. Please remember that the uplink frequency varies with on board temperatures. A lower temperature means a higher frequency!

EO88 – Nayif-1. EO88 continues to perform nominally and is switching between high power telemetry for educational outreach when in sunlight and to its U/V transponder mode when in eclipse. It will soon celebrate its 5th birthday in space after launch on 15th February 2017.

JO97 – JY1Sat. JO97 suddenly stopped transmitting telemetry data on May 1st last year. The cause of this anomaly is unknown but fortunately the U/V transponder continues to operate continuously.

Battery voltage and incoming solar current over time – daily average