Why can't assign the applicationimpersonation in exchange 2010?

This is using MS Exchange Server 2010 with SP1, in MS Windows 2008 r2-based AD Domain. We want to assign the role - applicationimpersonation to a service account. Please see steps (powershell) we conducted as follows:

    a.  type - get-managementrole -roletype applicationimpersonation

         result: <blank>

   b. type - new-managementscope -name resourcemailboxes -recipientrestrictedfilter: recipientfilter

       result: no problem

   c. type - new-managementroleassignment -name resourcesimpersonation -role applicationimpersonation -user <service account>  -customrecipientwritescope resourcemailboxes

      result: error - The "applicationimpersonation" management role can't be found. Check the role entry name, and try again.

What's missing. Does this applicationimpersonation does not exist?