The error messages says it all:
JAVA_HOME should point to a JDK not a JRE.
The difference between a JDK and a JRE is that the former is a complete development environment (Java Development Kit) that includes, among other things, the java compiler and the java archiver whereas the JRE (Java Runtime Environment) is only for running applications that have already been compiled and packaged as a jar archive. A JDK includes a JRE but the reverse is not true. The
mvn command stands for maven and it will take care of downloading the required libraries (i.e. Hipparchus), install them, and launch the java compiler to compile the sources and then launch the java archiver to package them and create the orekit-10.1.jar file. For at least these two steps, maven needs a JDK.
So you should check that you installed a full JDK and that your JAVA_HOME environment variable points to its location.