Is Sentinel-3 good enough... for ice?
Sentinel-3 can certainly do a job, and with funding already in place to fly four of these satellites Europe's radar observations of a changing Antarctic can continue unbroken into the 2030s. That'll represent an unambiguous climate trend of more than 40 years.
The question for the European Union and its technical partner, the European Space Agency, is whether they could do even better?
The Cryosat spacecraft - as its name suggests - is a specialised ice-monitoring satellite. It was an experiment with dual-antenna technology that outperforms all other radar altimeters in those hard-to-sense mountainous locations.
It also flies closer to the pole, allowing it to see more of the ice sheet.
And that's vital not just in Antarctica but also at the other end of the planet, where the Sentinel leaves a large "data hole" that cuts off the top of Greenland.
"Mass loss in the northern part of Greenland has set in during the past years and as the polar amplification is leading to higher temperature rise in the north, it is absolutely crucial for mass loss estimates in the next decades to have an instrument that is covering the north of Greenland," Prof Angelika Humbert from the Alfred Wegener Institute in Bremerhaven, Germany, told BBC News.
European research ministers at the end of the year will be presented with the option to pursue a Cryosat follow-on mission, which currently has the codename of Cristal.
"Ground processing can be upgraded after launch, but not the altimeter itself," commented Dr Amandine Guillot from the French space agency (Cnes)
"That's why, for example, the Sentinel-3 altimeter is not able to retrieve as much data as Cryosat over the coastal zone of Antarctica.
"That is why the Cristal mission, which has the primary objective of ice monitoring, has a real added-value with respect to the Sentinel-3 mission."
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter:@BBCAmos