The time limit for. shipping a POV is the same as for travel and HHG transportation limits (JTR Para 5366, POV. Transportation Time Limitation), 1 year from the date of retirement/separation with severance. pay or 180 days from the date of separation.
The envelope is the large bag that holds the helium gas. The envelope is generally cigar-shaped, for aerodynamic purposes, and made of a durable, airtight, lightweight fabric (polyester composites) that is much like the fabric of a space suit.
In this case, the helium balloon that you hold by a string is floating in a. pool of air (when you stand underwater at the bottom of a swimming. pool, you are standing in a pool of water maybe 10 feet deep -- when. Center for Cosmological Physics 2002 Yerkes Winter Institute Balloon Laboratory - 2.