I attended a conference this week where space weather was a big topic of discussion. There is serious concern in the weather community about the loss of capability that they are facing. SOHO won't last forever (it's already at or beyond the predicted end of life and has several degraded systems) with no replacement scheduled. Without SOHO, the only way to monitor CMEs and other sun-related events will be an old and hard to maintain network of terrestrial solar telescopes.

Likewise, when the ACE satellite dies (as it almost did during a massive X-ray event a year or so ago), there won't be any systems to monitor interplanetary space environment conditions. That might not seem to be a problem, but in fact, it has an impact on current space systems.

I've been pondering how difficult it would be to develop a solar corona telescope as a secondary payload to GOES satellites. It could be mounted on the solar array yoke. The real difficulty would be integrating the telescope with the existing GOES systems. The interfaces to the TT&C system would be pretty simple - you'd need to send a few commands and transmit a few telemetry points. Likewise, the interface to the electrical power system would be pretty simple. The challenge would be integrating the telescope's data stream into the GOES satellite downlink signal. You'd need to transmit a lot more data than is currently the case. That might require some pretty extensive upgrades like a more powerful transmitter and/or a higher gain antenna. Going with a higher gain antenna would mean tighter pointing accuracy as well as upgrades to the ground data handling equipment and perhaps the software. Such an upgrade might end up costing something on the order of $50 million or so for the complete package. Not cheap, but cheaper than launching a new dedicated solar observatory - with the possible exception of a dedicated microsat launched as a secondary payload on a commsat. Such a microsat might weigh less than 100 KG.