Launch Delays Blessing in Disguise for GRACE-FO Mission

GRACE-FO spacecraft (Credit: Airbus Defense and Space)

A German-American science mission scheduled to launch this week is running nine months behind schedule due to issues with launch vehicles. However, the delays turned out to be a blessing in disguise for the project, according to a Government Accountability Office (GAO) assessment.

The twin Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) satellites are set to launch on Tuesday at 12:47:58 p.m. PDT (3:47:58 p.m. EDT; 1947:58 GMT) aboard a SpaceX Falcon 9 booster from Vandenberg Air Force Base in California. The launch will be webcast at www.nasa.gov and www.spacex.com.

GRACE-FO, which is a joint project of NASA and the German Research Centre for Geosciences (GFZ),  will measure Earth’s gravity field and provide insights into water movement on and beneath its surface. The satellites will expand upon the GRACE satellites, which flew a five-year science mission after they were launched in 2002.

GFZ, which was responsible for the launch vehicle, originally booked a Russian Dnepr rocket for an August 2017 launch, GAO found. When Roscosmos said the rocket was no longer available, the center arranged the flight on the Falcon 9, which will also launch five Iridium-NEXT communications satellites on Tuesday.

The initial four-month launch delay caused by the change was extended further when a Falcon 9 exploded on the launch pad while being fueled for an engine test on Sept. 1, 2016. Additional delays pushed back the flight to this month.

The nine-month schedule slip turned out to be good news for the GRACE-FO mission.

“The project used the extra time in the schedule due to launch delays to conduct additional risk reduction activities during system-level integration and test,” the report stated. “For example, the project identified a design issue with its global positioning system antenna during testing. With the extra time, it replaced the antennas on both spacecraft to resolve the issue.

“In addition, the project identified a manufacturing issue with one of the two cavities that stabilizes the laser of its Laser Ranging Interferometer (LRI), which is contributed by GFZ….With the extra time, the project was able to replace and reintegrate the cavity with the spacecraft,” the report added.

Engineers also had time to investigate the shifting of an optical system component of LRI that occurred during system-level environmental testing in August 2017.

“The project expects that it will be able to use the component as-is because tests indicate there is sufficient performance margin even with the shifting, that exposure to the vacuum of space will reduce the shifting, and it can make operational adjustments to further improve performance, if needed,” the assessment found.

Project officials expect to launch the satellites within GRACE-FO’s cost baseline by using funding held in reserve to cover additional costs that resulted from the schedule slip, according to the assessment.

The GAO’s assessment of the project is below.

NASA: Assessments of Major Projects
Government Accountability Office
May 1, 2018
Full Report

Gravity Recovery and Climate Experiment Follow-On (GRACE-FO)

The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) will continue and expand upon the 2002 GRACE mission, which ended science operations in October 2017. The system, which consists of two spacecraft working together to obtain scientific measurements, will provide high-resolution models of Earth’s gravity field and insight into water movement on and beneath the Earth’s surface for up to 5 years. These models will provide rates of ground water depletion and polar ice melt and enable improved planning for droughts and floods. GRACE-FO is a collaborative effort with the German Research Centre for Geosciences (GFZ).

Project Information

NASA Lead Center:
Jet Propulsion Laboratory
International Partner: German Research Centre for Geosciences (GFZ)
Launch Location: Vandenberg Air Force Base, CA
Launch Vehicle: Falcon 9
Mission Duration: 5 years
Requirement Derived from: NASA 2010 Climate Plan
Budget Portfolio: Science, Earth Science

Project Summary

The GRACE-FO project plans to launch in May 2018, 3 months later than its committed launch readiness date of February 2018, but within its committed cost baseline. Delays to the project’s launch readiness date, which over time have accumulated to 9 months of delays, are related to the project’s launch vehicle arrangement. First, GFZ—NASA’s partner on the project, which is responsible for the launch vehicle—reported that it was notified by the Russian Federal Space Agency that the Dnepr launch vehicle was no longer available.

Subsequently, GFZ arranged to launch the two GRACE-FO spacecraft, along with commercial satellites, on a SpaceX Falcon 9. But the project experienced subsequent delays after SpaceX experienced an anomaly on a launch pad that resulted in delays to the launch schedule. The project used the extra time created by the launch delays to conduct additional risk reduction activities during system-level integration and test.

Cost and Schedule Status

Credit: GAO

The GRACE-FO project plans to launch in May 2018, 3 months later than its committed launch readiness date of February 2018, due to delays related to its launch vehicle arrangement. The project expects to launch within its cost baseline and plans to use its remaining project-held reserves to cover costs through May 2018. The project completed system-level testing on both spacecraft in November 2017 and shipped GRACE-FO to Vandenberg Air Force Base in California for pre-launch activities in December 2017.

Credit: GAO

Launch and Development Partner

The GRACE-FO project previously planned to launch early in August 2017, but delays related to its launch vehicle arrangement resulted in a 9-month delay to its launch readiness date. The launch vehicle is the responsibility of NASA’s partner on the project—GFZ. An initial delay of 4 months occurred when the project changed its launch vehicle after GFZ reported that it was notified by the Russian Federal Space Agency that the Dnepr launch vehicle was no longer available.

GFZ, in June 2016, arranged to launch the two GRACE-FO spacecraft, along with commercial satellites, on a SpaceX Falcon 9. SpaceX then experienced an anomaly on a launch pad in September 2016 that resulted in delays to the launch schedule as SpaceX investigated the source of the anomaly.

In July 2017, a new 30-day launch readiness window from March to April 2018 was negotiated, resulting in an additional 4 months of delays for the project. In March 2018, the launch was delayed an additional month to May 2018 due to launch range availability.

Integration and Test

The project used the extra time in the schedule due to launch delays to conduct additional risk reduction activities during system-level integration and test. For example, the project identified a design issue with its global positioning system antenna during testing. With the extra time, it replaced the antennas on both spacecraft to resolve the issue.

In addition, the project identified a manufacturing issue with one of the two cavities that stabilizes the laser of its Laser Ranging Interferometer (LRI), which is contributed by GFZ. LRI is a technology demonstration that performs the same ranging measurements of GRACE-FO’s microwave instrument but with greater precision and is not needed to meet the mission’s science requirements. With the extra time, the project was able to replace and reintegrate the cavity with the spacecraft.

In addition, the project is investigating the shifting of an optical system component of LRI during system-level environmental testing in August 2017. The project is investigating the cause, but anticipates the shift is likely due to the expansion of adhesive bonds between the optical components when exposed to temperature and humidity.

The project conducted additional tests using spare flight hardware in a vacuum, which removes humidity, to understand future alignment performance in a space-like environment. The project expects that it will be able to use the component as-is because tests indicate there is sufficient performance margin even with the shifting, that exposure to the vacuum of space will reduce the shifting, and it can make operational adjustments to further improve performance, if needed.

Project Office Comments

GRACE-FO project officials provided technical comments on a draft of this assessment, which were incorporated as appropriate.

  • Jeff2Space

    Sometimes you win the schedule chicken game, sometimes you lose. Looks like this time it’s a win despite the delay. Better to find these issues and fix them on the ground than to discover them in orbit.