"Stay tuned for March 8," Lau tweeted, with a similar-looking photo from the Apollo 8 mission.
The company is set to launch three new smartphones -- the OnePlus 9, 9 Pro, and 9R -- and a smartwatch this month.
OnePlus 9 Pro is tipped to come with 65W wired fast charging, which is found on the OnePlus 8T.
The OnePlus 9 Pro will also support reverse wireless charging. This feature can be used to charge accessories such as Bluetooth headphones, or a smartwatch.
Android Authority reports that OnePlus 9 is expected to have a 6.55-inch, 120Hz 1080p display, while the 9 Pro will have a 6.78-inch, 120Hz 1440p display.
Both devices are likely to house Qualcomm's Snapdragon 888 chip.
The cheaper OnePlus 9R (or OnePlus 9 Lite) may come with Snapdragon 865 processor.
OnePlus 9 Lite will borrow a lot from the recently launched OnePlus 8T. It may feature a 90Hz or 120Hz AMOLED display, and a quad-camera setup similar to the OnePlus 8T.