July 17, 2017 by Chris Bergin and William Graham

NASA and Boeing are reviewing the status of the TDRS-M launch date following an incident relating to an antennaduring the spacecrafts final launch processing to launch. The spacecrafts launch atop United Launch Alliances Atlas V rocket is currently scheduled to take place on August 3.

TDRS-M:

A flagship launch of the third of the latest generation ofTracking and Data Relay Satellites (TDRS) is facing a review following an incident during closeout processing.

The spacecraft has been preparing for an August launch inside the Astrotech Space Operations facility in Titusville, Florida.

No specifics about the July 14 incident have been provided, with a NASA statement only noting the assessments surround the spacecrafts Omni S-band antenna.

NASA and Boeing are reviewing an incident that occurred during final spacecraft closeout activities, NASA said. The mission team is developing a plan to assess flight acceptance and the schedule forward.

These additional activities are under evaluation for a planned TDRS-M launch Aug. 3, 2017, on an Atlas V rocket from Cape Canaveral Air Force Station in Florida.

It is understood this latest incident is not related to a close call that NASA was investigating earlier in the flow. That incident involved the spacecrafts shipping container containing environmental instrumentation which slid a couple of feet on the trailer it was being winched on to.

The processing flow for the mission had already passed several review milestones, specifically the Launch Vehicle Readiness Review (LVRR), Safety and Mission Success Review (SMSR) and the Calibration & Recertification Review (CRR).

The Atlas V that will provide the spacecraft with its ride to orbit is currently being integrated inside the Vertical Integration Facility (VIF) at Space Launch Complex -41 (SLC-41). ULAs flow with the rocket has continued without issue, with the TDRS issue unrelated and upstream to their operations.

The next key milestones in the flow are the Atlas V/TDRS-M MORR (Mission Operations Readiness Review), TDRS-M FRR (Flight Readiness Review) anda final status review, the latter set to take place on July 28.

This will clear the way for Atlas V to launch with TDRS-M on August 3, in a window ranging from 09:02 to 09:42 Eastern, pending the recent incident hasnt caused a delay to the launch date.

The mission will be the 13th spacecraft in NASAs Tracking and Data Relay Satellite System (TDRSS), with TDRS-M becoming the final spacecraft in the set of three third-generation satellites.

The new range are 3,454 kilogram (7,615 lb) satellites which have been manufactured by Boeing and based around the BSS-601 satellite bus.

They have a design life of 15 years. However, todatemost TDRS satellites have significantly exceeded their design expectations. The satellite carries an R-4D-11-300 apogee motor to raise itself into its final orbit and carry out othermaneuvers.

TDRS-M is powered by solar panels, generating between 2.8 and 3.2 kilowatts of power depending on illumination.

The satellite carriess-bandphased array antennae to allow simultaneous communications with five other spacecraft, as well as two steerable antennae providing S, Ku or Ka band coverage to spacecraft requiring communications at a higher data rate. Its this system that is currently being reviewed due to the incident noted by NASA over the weekend.

History of TDRS:

TDRS satellites are used by NASA to provide communications links between spacecraft in orbit includingthe International Space StationandHubble Space Telescope and ground controllers. Part of NASAs Space Network, TDRSS was implemented to reduce NASAs dependence on ground stations and airborne tracking assets.

Use of the network is not restricted to NASA missions; amongst other users United Launch Alliance and others use TDRS to relay data from their rockets during launch, JAXA and the European Space Agency have used TDRS for missions, including HTV and ATV flights to the ISS, and the system is rumoured to be used by the National Reconnaissance Office to supplement its own Satellite Data System, transmitting data from reconnaissance satellites for analysis.

Older satellites in more highly-inclined orbits have been used to relay communications to the AmundsenScott Station at the South Pole; a site not usually accessible to communications satellites due to its extreme latitude.

First-generation TDRS satellites were deployed from the Space Shuttle, with an Inertial Upper Stage used to raise them into geostationary orbit. These spacecraft, whichwerebuilt by TRW, were designed for a seven-to-ten year service life.

The first TDRS satellite TDRS-1 was deployedduring STS-6, the maiden flight of Challenger, in April 1983.

During the launch ofTDRS-1the Inertial Upper Stage malfunctioned. A two-stage solid-fuelled vehicle, the first stage of the IUS performed nominally however during the second stage burn control of the vehicle was lost.

The satellite was deployed into an orbit with a perigee approximately 13,000kilometers(8,000 mi, 7,000nmi) below geosynchronous orbit, with its period five and three-quarter hours shorter than expected.

Despite this partialfailurethe satellite was able to recover to its operational orbit, making a series of firings with itsmaneuveringthrusters which gradually raised the perigee over the period of several months. TDRS-1 exceeded its design life almost four times over, finally being decommissioned in June 2010 after its final amplifier failed.

Following the malfunction during the TDRS-1 launch and anomalies on several other flights, concerns over the reliability of the IUS resulted in knock-on delays for the TDRSSprogram. STS-12, which had been slated to deploy the second satellite, TDRS-B,was canceled and the payload reassigned to STS-51-E.

Challenger was rolled out to Launch Complex 39A in February 1985;howevera faulty timer in the TDRS satellite forced NASA torollbackanddestackthe orbiter. STS-51-E wascanceled, withChallenger flying the STS-51-B mission instead.

TDRS-B was finally ready to fly in early 1986, as the primary payload of STS-51-L. Launched on 28 January,Challenger disintegrated 73 seconds later with the loss of her crew and payload.

As a result of the failure, the designation TDRS-2, which would have been given to TDRS-B upon the completion of initial on-orbit testing, was never assigned typically for a program with separate launch and on-orbit designations in the event of a launch failure the on-orbit designation is reassigned to the next successful mission to avoid gaps in the sequence.

When Space Shuttle missions resumed in 1988,TDRS-3 was the primary payload for the return-to-flight mission, STS-26, flown by Discovery. TDRS-3 remainsoperable,and is located at 49 degrees west as a reserve satellite.STS-29, also flown by Discovery, successfully deployed TDRS-4which operated until late 2011 and was decommissioned in March 2012.

TDRS-5 was deployed by Atlantis during STS-43, withEndeavour launching TDRS-6 during STS-54; these two spacecraft, the last from the original order, remain in operation located at 161 degrees west and 62 degrees west.

The last first-generation satellite, TDRS-7, was ordered as a replacement for TDRS-B and incorporates some enhancements over the other satellites, while still being based on the same TRW bus.

It was deployed by STS-70 in1995,and remains in operation at 85 degrees East (275 degrees West) as TDRS-Z, covering the so-called Zone of Exclusion between the operational West and East satellites; TDRS-9 and TDRS-10.

Three second-generation TDRS satellites were built by Hughes Space and Communication, later part of Boeing, and launched between 2000 and 2002. These BSS-601-based spacecraft were launched by Atlas IIA rockets.

TDRS-8 was found to have a defective antenna, resulting in reduced performance compared to expectations before launch.

The TDRS-9 and 10 spacecraft suffered from the same fault, however as a result of the problem with TDRS-8 it could be found and corrected while they were still on the ground.

TDRS-9 also suffered from apressurizationproblem in its propulsion system, which resulted in it taking six months to reach its operational orbit. TDRS-9 and 10 are located at 41 degrees and 174 degrees west as the operational TDRS-East and TDRS-West satellites respectively. TDRS-8 is located at 89 degrees east (271 degrees West).

The first two third-generation satellites were ordered in December 2007, with the contract including options for NASA to order two further spacecraft. TDRS-11, known as TDRS-K at the time of launch, was the first third-generation satellite to fly riding an Atlas V into orbit.

TDRS-L, the second of the original two orders, while one of the options was exercised in late 2011 at a cost of $289 million. That satellite, TDRS-M, is the one to be launched next.

The three primary satellites in the constellation are the TDRS-East, TDRS-West and TDRS-Z satellites;howeverall of the operable spacecraft aside from TDRS-3 are in operational use.

(Images via NASA, ULA, Boeing and L2 Historical.To join L2, click here:https://www.nasaspaceflight.com/l2/)

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TDRS-M launch date under review following pre-launch incident - NASASpaceflight.com