NPP arrives on final orbit, enjoys early success ahead of pathfinder operations

by Chris Gebhardt

After making a successful trip to Earth orbit aboard the stalwart Delta II rocket, the NPP satellite has enjoyed tremendous early success with the startup of its numerous instruments and initial test of its data gathering capability – the initial results of which have already been released. The spacecraft officially reached its final orbit station on Thursday.

Post-launch success: NPP to usher in new era of weather monitoring:

Intended to help usher in a new era of weather surveillance from Earth orbit, the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite team got right to work activating the spacecraft’s systems following a highly successful and spectacular launch on the thought-to-be retirement flight of Delta II rocket.

According to the first NPP on-orbit operations report filed October 28, 2011, just over 15 hours after the satellite’s launch, “NPP is looking good!

“Accomplishments: Successful GPS turn on and lock; Solid State Recorder (SSR) Memory dump as part of SSR configuration; controlling transmitter configurations for TDRSS and Svalbard via on-board stored commands; playbacks via stored commands for Data Storage Unit (DSU); continued heater configurations; and satellite Earth Point achievement,” noted the mission report – available for download on L2.

In all, very few issues and anomalies were experienced in the first few orbits of NPP’s lifespan. Moreover, the issues and anomalies faced by NPP team in the first 15 hours of operation were very minor, with the main bulk of attention being a “not as expected” activation of the GPS (Global Positioning System) sequence.

As noted by the October 28 report, the first attempt to activate the GPS sequence to obtain a lock on the spacecraft was prematurely cut off.

While a shutdown and reactivation of the system was completed, the second attempt to obtain a GPS lock on the NPP satellite was successful if not completely normal.

“Second attempt to lock GPS was successful though the signature was not full nominal – investigation is ongoing (may have been a procedural issue or a product issue),” noted the status update.

Additional notes within the first 15 hours of on-orbit life revealed a minor issue with the White Sands pre-processors which had previously displayed a tendency to “not send VC2 data.”

Moreover, the Mcubed experiment was shown to be transmitting telemetry that was unable to be decoded.

But aside from those minor issues, all systems aboard the spacecraft were reported to be “healthy and working very well.”

This excellent trend continued through the first 48 hours of NPP’s orbital journey. Within 48 hours of arriving on orbit, NPP was revealed to be “doing well and in Mission Point mode with all instruments off (heaters on survival mode).”

By this point, primary and secondary Catbed heater verifications had been performed as had a Delta-V maneuver checkout.

This Delta-V maneuver checkout was accomplished by a “slew maneuver to nominal Delta-V attitude and returned to nadir pointing (first maneuver of the spacecraft in Mission Point mode),” noted the October 30 spacecraft status update.

By this point in the mission, no notable issues or anomalies had occurred on the spacecraft since its initial checkout report 15 hours after launch.

Delta II/NPP FRR Article:
Delta II/NPP Launch Article:

This good fortune continued into the first full week of operations for NPP as teams on the ground continued to activate the satellite’s on-orbit systems.

By November 1, the open loop test burn had been completed.

As noted by the November 1 status update, also available for download on L2, “The first closed loop test burn/calibration burn is scheduled for this morning (November 1).  This burn is a 30 sec long burn.  It is also long enough that the orbit team will be able to get a calibration on the actual thruster performance.”

Following this burn, the spacecraft and ground control teams did experience a Stored Commands issue, and by November 5, troubleshooting and recovery efforts were well underway and a solution quickly identified.

“Implemented revised validation process for Stored Command loads to ensure no omitted commands,” noted the November 5 spacecraft status update.

“Raytheon factory was able to replicate command omission and determined root cause.  Mission Planning load generation procedures revised to eliminate root cause trigger.  The next Stored Command load was successfully built, validated, and uploaded using revised generation and validation procedures.”

With this issue fixed, initial activation of the NPP satellite’s instruments began on Monday, November 7 following a raising of NPP’s orbit.

By November 8, one of the spacecraft’s instruments, the ATMS, had completed a “full science data” collection run.

This was the first data collected by the satellite, and based on a successful launch an initial activation of spacecraft systems, several dates were subsequently solidified for “first valid science data acquisition.”

Currently, the first valid science data retrieval from the four remaining science instruments on NPP are expected on November 24 from the VIIRS, on December 10 from the CERES, on December 10 from the OMPS, and on December 11 from the CrIS instruments.

By November 9, the NPP team had activated three of the five science instruments on NPP, and the spacecraft as a whole was reported to be functioning nominally.

During initial activation of the VIIRS instrument, however, an indication of a “single software overrun processing error” was reported.  The status update quickly noted that “A few errors of this type were observed during NPP Compatibility Test Part 1 and Satellite T/V and have no impact on VIIRS performance.”

All five of NPP’s instrumentation packages were activated by November 10.

Complete instrumentation activation and functional check out was scheduled to be completed by November 15, as was spacecraft inclination Delta-V and multiple raising burns.

And while the spacecraft has performed exceptionally well during its first two weeks in orbit, one cannot overlook the ground personnel responsible for getting the satellite up and running following its launch.

As related by one of the mission managers for the NPP project, “Awesome job by the extended NPP team. Less than 2 weeks into the campaign and we have a nominally functioning Observatory.”

“On behalf of the outstanding Ops, engineering, and ground teams, I am happy to say we now have a fully operational Observatory.  We just need to finish getting the Satellite to its final on orbit station and finish configuring the instruments for science over the next month.”

NPP finally reached its final on orbit station at 12:48pm EST on Thursday.

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