The Apollo Program
First of the Apollo J mission series which were capable of longer stay times on the Moon and greater surface mobility, Apollo 15 had four primary objectives which fall into the general categories of lunar surface science, lunar orbital science, and engineering/operational.
The mission objectives were:
Exploration and geological investigations at the Hadley-Apennine site were enhanced by the addition of the lunar roving vehicle that allowed Scott and Irwin to travel greater distances from the LM than they could on foot during their three EVAs. The Apollo lunar surface experiment package (ALSEP) was the third operating ALSEP along with Apollo 12 and 14.
Orbital science experiments were primarily concentrated in an array of instruments and cameras in the scientific instrument module (SIM) bay of the spacecraft service module. Command module pilot Worden operated these instruments during the period he was flying solo and again for two days following the return of the astronauts from the lunar surface. After transearth injection, he went on an EVA to retrieve film cassettes from the SIM bay.
Engineering and operational tasks the Apollo 15 crew carried out included , 1) evaluation of the modifications to the lunar module which was made for carrying a heavier payload and for a lunar stay time of almost three days, 2) changes to the Apollo spacesuit and to the portable life support system, and 3) performance of the LRV.
From Apollo 15 Press Kit.