Rocket Lab has delayed its "Make it Rain" launch until 4.30pm Saturday at the earliest.
A seven-day launch window opened on Thursday, but the first launch attempt was stood down for further checks of ground equipment. Checks continue today.
The Herald will carry a livestream of the launch.
Wairoa District Council has allocated a viewing area for the public near Nuhaka, accessible via Blucks Pit Road - around 20km from the launchpad.
The "Make it Rain" mission (named for a client in rainsoaked Seattle, with a nod to NZ weather) will carry satellites for US Earth-imaging company Blacksky, the Melbourne School of Engineering-backed Melbourne Space Program (whose students have created an experimental cubesat) and two "Prometheus" birds for US military's Special Operations Command (Socom).
Socom - best known for the "Blackhawk Down" incident in Somalia - coordinates between Special Operations units in different branches of the US military.
Rocket Lab has not been keen to talk about the Socom satellites, which have been left off promotional material on its website.
But Rocket Lab boss Peter Beck says they are part of a research rather than operational mission.
NZ Space Agency head Peter Crabtree also declined to detail the Socom payload, but said it had been signed off by the NZSA and the minister in charge of the agency, David Parker. (For more, read, Expert's best guess at Rocket Lab's secret military payload).
Rocket Lab has already launched satellites for US defence agency Darpa and the US Air Force this year.
Crabtree said all Rocket Lab payloads have to pass a safety test, for where the NZSA is typically satisfied to take its lead for a "competent offshore agency" in the US or Australia. Practical factors are assessed such as the risk of debris.
A more abstract "national interest" test is also applied. Crabtree said it includes consultation with MFAT, security agencies and the NZDF.
Earlier, Beck said most defence technologies were "dual use". Technologies that had come out of defence spending, including the internet, GPS and imaging systems that can help monitor and inform decision about global warming all gelled with his company's motto that "We go into space to improve life on Earth."
The launch will be the Electron's seventh overall and the fourth this year.
Beck says Rocket Lab is still pushing toward its goal of a mission a month, and still hopes to showcase its ability for a launch a fortnight by the end of this year - and is looking to boost staff its New Zealand-based staff by 100 ASAP (the company currently employs around 500, with around 400 in NZ) with many general roles to fill.
The CEO says Rocket Lab's first launch complex outside of New Zealand - which is being constructed inside Nasa's Wallops facility in the US state of Virginia - is on track for completion by the end of this year.
Beck says the pipeline for Virginia is all US government clients who require a local launch. Rocket Labs will continue to use Mahia - which is currently being upgraded and expanded - as its high-volume launch facility.