It looks like some kind of testing equipment used probably when the plane was parked, maybe testing the nose-wheel hidraulic system? Because that canister looks like it's attached to some kind of trolley that fits the front part of this DC-9, well this is just a guess!
Interesting to see that this aircraft crashed latter and also it was good to see some nice old DC-8's. I can identify a Braniff, a SAS and an Air Canada.
CV990, the Maserati of the skies!