What approach do you need for hyper spectral data? classification or other approaches?

you can freely download HSI data for classification approach from below link.

http://www.ehu.eus/ccwintco/index.php/Hyperspectral_Remote_Sensing_Scenes

Pls check USGS Website

For ground data you need to visit the area of your interest. Also you must have the idea for which specific purpose you want to do ground truthing. Set the target and take all the necessary devices to record the data and validate with Hyperspectral data. This is what I understood from your query.. Thanks

I think USGS Website would be the good solution. Open an account and order your data with map grid and time based on satellite image taken. They will send you those files. Hope, you will receive all required raw image data.

You can also get hyperspectral data from Bhuvan.