SpaceX launches Intelsat 40e with NASA’s TEMPO instrument

by Anthony Iemole

SpaceX has launched its 23rd mission of 2023 with the company’s Falcon 9 rocket lofting the Intelsat-40e/TEMPO payload to a geostationary transfer orbit (GTO). Liftoff of the Intelsat-40e/TEMPO mission occurred at the opening of a 119-minute window at 12:30 AM EDT (04:30 UTC) on April 7 from Space Launch Complex 40 (SLC-40) at the Cape Canaveral Space Force Station (CCSFS) in Florida.

This mission was the second of what is expected to be another busy month for the launch provider as it continues to trend toward another record-setting year for launches.


Intelsat-40e is a high-throughput geostationary communication satellite that will provide focused coast-to-coast coverage to customers over North America. The satellite was built by Maxar Technologies and is based on the company’s 1300-class satellite platform. Intelsat-40e masses around 5,440 kg and is the 54th satellite built by Maxar for Intelsat, in a partnership that has lasted more than 40 years.

For this mission, the satellite will host an integrated payload for NASA, the Tropospheric Emissions: Monitoring of Pollution (TEMPO). TEMPO is a UV-visible spectrometer built by Ball Aerospace that will measure atmospheric pollution over North America. The instrument, about the size of a dishwasher, will allow the first hourly measurements of pollution across the continent during the daytime, allowing researchers to quickly and better understand changes in air quality.

TEMPO is the second of a three-instrument constellation designed to monitor air pollution on an hourly basis. The first, the Geostationary Environment Monitoring Spectrometer (GEMS) is a sister instrument to TEMPO and is mounted onto the Korean Aerospace Research Institute GEO-KOMPSAT-2B satellite which was launched on an Ariane 5 rocket in Feb. 2020 and allows measurements to be taken over Asia.

The final instrument of the constellation will be mounted onto the Sentinel-4 satellite. It is currently expected to be launched in 2024 and will provide coverage to Europe and Northern Africa.

Countdown and Launch

Friday’s mission saw Falcon 9 booster B1076 fly for its fourth time. This booster first flew back in Nov. 2022, where it helped loft Cargo Dragon C211 on the CRS-26 mission to the ISS. It then went on to fly the OneWeb #16 mission in January, followed by the Starlink Group 6-1 mission at the end of February where SpaceX launched its first batch of “V2 mini” Starlink satellites.

The weather was forecasted to be 90% go with the primary concerns being liftoff winds and the cumulus cloud rule, with identical conditions in the event of a 24-hour delay.

The launch mission execution forecast for the Intelsat-40e mission. (Credit: 45th Weather Squadron)

As per usual with Falcon 9 launches, a go/no-go poll was conducted at T-38 minutes to ensure everything remains “go” for propellant loading. With no issues reported with either the ground equipment, vehicle, or weather, propellant loading began at T-35 minutes with nearly one million total pounds of liquid kerosene, commonly referred to as RP-1, and liquid oxygen (LOX) slowly flowing into the vehicle.

RP-1 loading onto the second stage concluded around T-20 minutes, after which the transporter/erector (T/E) began to purge its propellant lines. This was visible by the presence of a large white plume emitting from just over halfway up the T/E and lasted approximately four to five minutes.

At T-16 minutes LOX loading began on the second stage and concluded at around T-2 minutes.

Falcon 9 began engine chill on the first stage around seven minutes before launch. This process involves flowing a small amount of propellant through the nine Merlin 1D engines located on the base of the vehicle to slowly cool them down to operating temperature to prevent any sort of thermal shock to the many components on the engines once the full flow of propellants is needed during startup and operation.

Around T-4 minutes and 30 seconds, the T/E opened up its two clamp arms from around the second stage.. Once open, the T/E retracted away just a few degrees to its pre-launch position.

The vehicle entered startup at T-1 minute and the launch director gave a final go/no-go for launch around T-45 seconds.

Falcon 9’s flight computer commanded the start of the nine Merlin 1D engines at T-3 seconds, during which the propellants flowed through the engines before finally being ignited by the use of an ignition fluid, Triethylaluminum-Triethylborane (TEA-TEB). This fluid is used due to being a pyrophoric reaction, meaning they ignite upon contact with oxygen. This reaction can sometimes be seen via the presence of a green flash just prior to the ignition of Falcon 9.

At T0, Falcon 9 lifted off and soon after began its gravity turn, flying due East from Cape Canaveral.

Max-q, the period of maximum aerodynamic stress on the vehicle, occurred a little over one minute into the flight, and MECO (main engine cutoff) occured around two minutes and thirty seconds after liftoff.

Just after MECO, stages one and two separated with the single Merlin Vacuum (M-Vac) engine igniting shortly after to burn for about six minutes to bring the vehicle into its initial parking orbit.

The TEMPO instrument in the cleanroom. (Credit: Ball Aerospace)

While this is occurring, stage one slowly reorients itself using onboard cold-gas nitrogen thrusters ahead of the entry burn.

B1076 conducted the usual entry burn seeing the vehicle ignite engines 1, 5, and 9 for a ~20-second burn to help slow it down as it enters the atmosphere.

Upon completion of the entry burn, the booster’s four hypersonic titanium grid fins steered it toward the drone ship A Shortfall of Gravitas (ASOG), positioned ~600 km downrange in the Atlantic Ocean.

The booster ignited its center engine, E9, for the final landing burn and deployed the four landing legs located around the base of the vehicle just before touchdown on the metal deck of the drone ship.

After stage two achieved an initial parking orbit, the vehicle coasted for a short time before igniting the M-Vac engine once more for a ~one-minute burn to raise the second stage’s orbit to a GTO.

Once complete, the onboard flight computer commanded the separation of the Intelsat-40e/TEMPO payload, after which the satellite will eventually unfold its solar arrays and use its own onboard propulsion to place itself into the final operating geostationary orbit ~35,786 km above North America.

(Lead photo: Falcon 9 launches Intelsat 40e with TEMPO. Credit: Julia Bergeron for NSF)

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