Not an astronomer but things you can do on the ground:
1. Bigass telescopes. Some radio telescopes are 100 or even 1000 feet across. You can't put something like that easily in a rocket fairing. JWST has a 20 foot mirror and they probably spent hundreds of millions of dollars figuring out how to fit that thing in an Arianne 5.
2. Easy maintenance and upgrades. There are 80 year old telescopes still doing useful science since you can make incremental upgrades over the years. (shoutout to Hubble: at 30 I think it's probably the longest lived space telescope, even if it's getting a bit long in the tooth)
3. Interferometry. This would potentially be really cool to do in space, since you could theoretically make a telescope whose diameter is tens of thousands of miles. However, interferometry requires you to be able to position yourself really accurately (amount of accuracy you need depends on wavelength and a few other factors, but potentially at the micro-meter level). That's really hard to do in space.
4. You can build a bunch of ground based observatories for the cost of a single space one.
5. Data downlink. Some telescopes generate a lot of data. It's not easy to get a terabit per second of data down to the ground.
1. Bigass telescopes. Some radio telescopes are 100 or even 1000 feet across. You can't put something like that easily in a rocket fairing. JWST has a 20 foot mirror and they probably spent hundreds of millions of dollars figuring out how to fit that thing in an Arianne 5.
2. Easy maintenance and upgrades. There are 80 year old telescopes still doing useful science since you can make incremental upgrades over the years. (shoutout to Hubble: at 30 I think it's probably the longest lived space telescope, even if it's getting a bit long in the tooth)
3. Interferometry. This would potentially be really cool to do in space, since you could theoretically make a telescope whose diameter is tens of thousands of miles. However, interferometry requires you to be able to position yourself really accurately (amount of accuracy you need depends on wavelength and a few other factors, but potentially at the micro-meter level). That's really hard to do in space.
4. You can build a bunch of ground based observatories for the cost of a single space one.
5. Data downlink. Some telescopes generate a lot of data. It's not easy to get a terabit per second of data down to the ground.