NASA is utilizing every cubic centimeter and every gram of available payload capacity in every planned Cygnus mission. But first time in its history, Cygnus will lift such large payload.
This mission will be exceptional not because of objective and payload (revealed amongst others in this post https://newsspaceflight.com/?p=10505). On 3rd December, Cygnus spacecraft named SS Deke Slayton II, will be launched in the extended version for the first time. It means that there will be around 3513 kg of supplies onboard for International Space Station. Comparing to previous versions of Cygnus, payload is extended with 1500 kg. Cygnus in enhanced version is also higher for about 1.2 m what gives an effect in increasing payload capacity from 18.7 to 27 cubic meters. Other significant change is adopting new, lighter solar arrays called by Orbital ATK Ultraflex. They are offering better power/weight ratio at 150 W/kg. Cygnus was showed to public last time on 14 November, before being covered with fairings and further mounting on atop Atlas V (Antares rocket which have been utilized usually with Cygnus, is not able to lift Cygnus enhanced). Information about the content of the payload is worth to supplement with additional details. Cygnus will lift among others: 227 kg of equipment for Extravehicular Mobility Units (Simplified Aid for EVA Rescue (SAFER) backpack unit, space suit gloves, batteries, a Liquid Cooling and Ventilation Garment (LCVG) and variety of tool bags). All equipment will be necessary for future installing International Docking Adapter (IDA) during EVA scheduled on 2016. Next 847 kg of payload will be covered by Space Automated Bioproduct Lab (SABL), research project targeted on wide range of life forms from bacteria to animal tissues. Nanorack nano satellite will be also onboard; it is first satellite designed to be deployed from ISS utilizing NanoRacks-MicroSat-Deployer (Kaber). Rest of payload weight will be divided between supplies for crew members (1181 kg), hardware for ISS (1007 kg) and computer parts for ISS (87 kg).