Here's the write up on Xbox Live about Commander Palmer if you wish to buy her armour for your XBL avatar. Gosh knows why you would buy it when it costs 320 MS points but that's not the point. The reference to Jun is:
"Once an ODST, Sarah Palmer was hand-picked by former Spartan-III Jun A-266 to be one of the first candidates in the new Spartan IV program. Quickly proving herself during the defense of the UNSC Infinity from a hostile takeover by Insurrectionists, Palmer was soon called upon to lead a Spartan strike team during the historic Battle of Draetheus-V. Now the senior Spartan aboard Infinity, Commander Palmer went on to be instrumental in the recovery of the Master Chief and the defeat of Jul ‘Mdama at Requiem."
Yes, yes, I hear you, the question is when did Jun hand-pick Palmer... Maybe that will be answered in Halo: Initiation.
Also did they just ruin the ending of season 2 of Spartan Ops? Cos I'm pretty sure thye did as the season left on a cliff hanger with Jul alive having snagelled one half of a very important key?