Rocket Lab launches NASA’s TROPICS satellites from New Zealand

by Justin Davenport

NASA’s Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) constellation, having switched launch vehicles after losing two satellites aboard an Astra Rocket 3.3 last year, has launched — this time aboard a Rocket Lab Electron rocket on a mission titled “Rocket Like A Hurricane” from Launch Complex 1B (LC-1B) in Mahia, New Zealand. Liftoff from LC-1B was on schedule at 13:00 NZST (1:00 UTC) on May 8.

Electron and TROPICS were originally set to launch during the week prior to the May 8th launch attempt. However, inclement weather delayed the launch to the following week.

The flight lofted the two TROPICS cubesats to a 550 km circular low Earth orbit inclined 32 degrees to the Equator. Therefore, Electron followed a trajectory slightly inclined to the northeast of the Mahia Peninsula. First-stage engine cutoff and separation occurred at around two minutes and 33 seconds after liftoff. Electron’s first stage was not recovered following stage separation.

The two TROPICS satellites and the Curie kick stage deployed at around nine minutes and 31 seconds after liftoff, with the kick stage igniting its engine just after T+30 minutes. The two satellites then deployed at T+33 minutes.

This mission is the first of two TROPICS launches this month from Rocket Lab and the fourth launch this year for Electron. The second TROPICS mission, named “Coming To A Storm Near You,” is scheduled to fly from Mahia in late May.  The TROPICS launches need to be completed within a 60-day period, hence the fast turnaround.

What’s more, the TROPICS launches were originally scheduled to fly from Rocket Lab’s Launch Complex 2 (LC-2) facility at Wallops Island, Virginia, but were switched to the Mahia launch site so that the TROPICS constellation’s four satellites could fly and be operational in time for this year’s Atlantic hurricane season, which officially starts on June 1.

The TROPICS project was approved in 2016 with a cost cap of $30 million. The mission is part of the NASA Earth Venture program, with William Blackwell of MIT serving as the mission’s principal investigator.

TROPICS was originally envisioned to be a constellation of 12 cubesats that would study the development of tropical cyclones, with a rapid revisit time to allow additional data gathering. However, the project ended up being reduced to seven cubesats, with the first being a pathfinder spacecraft.

Each 3U TROPICS cubesat, built by Colorado-based Blue Canyon Technologies, is equipped with a 12-channel passive microwave spectrometer that can provide imagery near 90 and 206 GHz, temperature soundings near 118 GHz, and moisture soundings near 183 GHz.

The measurements near 206 GHz will be useful for the measurement of cloud ice, while the seven channels near the oxygen absorption line at 118.75 GHz and three channels near the water vapor absorption line at 183 GHz will provide temperature profiles. The 90 GHz channel will measure precipitation.

Artist’s impression of one of the TROPICS satellites in orbit. (Credit: NASA)

These cubesats, each massing a little over five kilograms, measure 10 x 10 x 36 centimeters and are based on Blue Canyon’s XB3 cubesat bus. The satellites are powered by solar panels generating up to 27 watts of power and have an expected orbital lifespan of greater than five years.

The TROPICS satellites will be taking soundings of tropical cyclone activity on an hourly basis, and the data products are expected to improve our knowledge of how these storms evolve over time. This knowledge can improve intensity and direction forecasts.

Seven TROPICS satellites were built, with the first being a proof of concept demonstrator launched aboard the SpaceX Transporter-2 mission in June 2021. The first operational TROPICS launch occurred nearly a year later, on June 12, 2022, atop an Astra Rocket 3.3 on mission LV0010. However, complications with Rocket 3.3’s upper stage kept the satellites from reaching orbit.

Due to the loss of the first two TROPICS satellites, the revisit time projected for the constellation increased by 15 minutes, with only four satellites instead of the planned six. Four satellites is the minimum required for the scientific target of a one-hour revisit time to a given storm.

Cyclone Gabrielle from the NPP Suomi satellite. TROPICS will investigate storms like Gabrielle. (Credit: NASA)

Although there would actually be five TROPICS satellites in orbit after the two Electron missions from Mahia are completed, the pathfinder satellite launched in 2021 is in a polar orbit and not in the same orbital plane as the four that will be launched in the coming weeks. Should there be another mission failure for TROPICS, the remaining satellites could still be used for probing cyclonic storms, though the storm revisit rate would not be within the hourly target for the project.

The twin TROPICS launches hold a special meaning for Rocket Lab’s team, as Cyclone Gabrielle impacted nearby areas in New Zealand early this year. The storm killed at least 11 people and was the costliest cyclone in the Southern Hemisphere to date, causing at least $8.4 billion US dollars in damage. Rocket Lab assisted in local disaster relief efforts. Fortunately, the launch site at Mahia was undamaged by the storm.

(Lead image: Electron launches two TROPICS cubesats. Credit: Rocket Lab)

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