Implementation of Flight Dynamics Operations for 702SP ... · Thrust 68-71 mN (expected 79 mN) Cal...

Implementation of Flight Dynamics Operations

for 702SP Satellite using OASYS

April 21, 2016

ABS3A is a Boeing 702SP satellite with an all-electric propulsion system using 4

gimbaled Xenon propelled thrusters. Given the low thrust, the satellite performs 4

maneuvers daily. The presentation discusses the current OASYS v10.5.1b procedures

of Flight Dynamics and the differences between these procedures and the Boeing-

recommended implementation. Since the challenge was to successfully perform Flight

Dynamics operations using OASYS v10.5.1b, the presentation will highlight the

problems and challenges encountered during satellite handover and how these were

addressed in order to successfully migrate and implement ABS3A Flight Dynamics

Operations of 702SP functions with OASYS using Boeing-provided libraries.

1 INFORMATION IS CONFIDENTIAL AND ABS/KISI/BSS

PROPRIETARY 20-Apr-16

Implementation of Flight Dynamics Operations for 702SP

Satellite using OASYS

Subic Bay Satellite Control Center & Teleport

Geographical Location Longitude:120.279772 deg E

Latitude:14.759211 deg N

Located 150km away from

Central Manila

INFORMATION IS CONFIDENTIAL AND PROPRIETARY 3

Subic Bay Satellite Control Center

Home to Primary Satellite Operations

Satellite Controllers

Satellite Engineering team

Mission Analysis

Operations Systems

Ground System Engineers


Backup Satellite Operations Center

Located in Metro Manila

9/F Salcedo Tower, Makati City

Fully functional redundant satellite

operations center.

Satellite operations, mission analysis

and offline analysis capability.


ABS Satellite Fleet

2 Lockheed Martin A2100

2 Space Systems Loral FS1300

1 Space Systems Loral LS 1300

1 Boeing 702SP

1 Boeing 702SP launch scheduled for

second quarter of 2016


ABS Satellite Fleet

OASYS in ABS

ABS uses OASYS for four of its six satellites

ABS-2 / SSL FS1300

ABS-3A / Boeing 702SP

ABS6 / Lockheed Martin A2100

ABS7 / Lockheed Martin A2100

ABS-2A / Boeing 702SP (Planned)

Others

ABS3 and ABS4 use APS (SSL)



Four Gimbaled Xenon Propelled Thrusters

702SP has four 25 cm XIPS thrusters on the anti-

nadir face

Thrust 79mN

ISP 3400 sec low power

Performs 4 thrusts daily



Flight Dynamics Processes using OASYS



Reconstruction – T&C MUS Tool

The T&C MUS Tool is

used to collect telemetry.

It retrieves data from the

real-time/archive system.

Telemetry is processed

and files listing

temperature, pressure,

etc. are produced, which

are readable by OASYS.



Reconstruction – T&C MUS Tool Output Files



The ATD files, outputs of

the T&C MUS tool, are

transferred to a folder for

OASYS’s processing.

Reconstruction



During reconstruction, this looks for ATD files. All ATD files within the specified Start and End time will be included in the reconstruction.

The report files, thruster profiles, ASCII database files will be automatically produced and saved to the folders indicated.

Orbit Determination



Inputs:

Database

Ephemeris

Thrust Profiles*

Track files

* (Produced by Reconstruction)

During the OD, the Thrust

button in ephemeris

services must be turned on

to estimate for Ct of

performed thrusts.

Stationkeeping

Small orbital changes

Simultaneous orbit correction and autonomous momentum dumping (A burns and B burns)

Maneuver planning cycle typically 2 weeks to 4 weeks with minimal ground intervention

XIPS thrusters point toward the general vicinity of the satellite cg

Inclination control by delta V component in normal direction

Eccentricity control by delta V components in radial and tangential directions

Drift control by delta V components in tangential directions



Station Keeping Planning

Boeing Recommendation: Upload 16 days of plan; Re-upload every 2 weeks

ABS Practice: Upload 30 days of plan; Re-upload every 2 weeks; Remaining days act as buffer

JD base time

- Changed bi-annually to place move eclipse exclusion zone at station keeping boundary

- Right ascension of +pi()/2 from winter to summer solstice; -pi()/2 from summer to winter

solstice

JD Plan Time

- Burn plan calculation time occurring at the same orbital position per day

- We use the 7-day (week) average for the MOM Cmd Dump Vectors and the Filtered MOM

Arm Errors for our maneuver planning.



OASYS XSK



Inputs:

Database

Ephemeris

The XSK plans for

the duration of the

ephemeris. The

control parameters

can be modified in

the database.

Report files, plan

thrust profiles, plan

ephemeris will

automatically be

generated and

saved in the

specified folders.

XBU



Inputs:

ATD file from XSK

plan

Convert the plan to

buffer upload file

Sample XBU for Upload



Maneuver Plots - Longitude





Maneuver Plots - Inclination



Maneuver Plots - Eccentricity

No Burn Days Specified by Ground

No burn day must be intentionally set during planning in eclipse of the Sun by the Moon events;

OASYS can not avoid such event.

ABS has not yet encountered a no burn day. One eclipse of the Sun by the Moon occurred inside

an eclipse of the Sun by Earth, as seen above.



BBS_UI in OASYS Database





BBS_UI in OASYS Database

Timeline of Events during ABS3A Handover



Timeline

Sept 1, 2015

Start of OJT with Boeing Astrodynamics; Boeing Astrodynamics Person arrives in Subic

2-Station Ranging biases were established

Difficulty transferring ABS3A track files from sbsvr4 to sboas3 using Task Initiator. Initial workaround is a batch file on sboas3 Desktop called "FTP_trk_file.bat" that will get all the ABS3A track files from the server and put it on C:\ISI\FTP\abs3a folder of sboas3 machine

Sept 2, 2015

XBU and SCE tables generated by Boeing were uploaded

Sept 3, 2015

XIPS burns day 1 of Table 1 (Uploaded Table on Sept 2) has been generated by the spacecraft



Timeline

Sept 3, 2015

ABS3A CLMA Antenna, EPOCH is giving a wrong timestamp on the data

Momentum had accumulated during the execution of burn table 1 day 1 maneuvers so

manual momentum burns were needed.

Manual Momentum Burn 1 : September 3, 2015 19:54 – 20:01




These were executed by Boeing MCC after the Burn 4 of previous day’s Burn Table

(TB1-D1) and prior to Burn 1 of the current Burn Table (TB2-D2).

Ephemeris Table Index 3 has failed Sudden Jump Test.



Timeline



Manual Momentum Burns Performed on Sept 3, 2015

Timeline

Sept 4, 2015

One cycle of Reconstruction and Orbit Determination is taking at least 5-6 hours to finish.

ABS informs ISI regarding the large amount of data in ATDs produced by the T&C MUS

tool. ISI remotely logs in to modify T&C MUS tool to adjust tolerances used in data

gathering for maneuver reconstruction and thruster profile.



Timeline



Timeline

Sept 5, 2015

ABS FD found errors in reconstructed maneuvers. GXP angles from MUS Tool were in

degrees but the unit indicated is radians. Hence, OASYS reads inputs as radians instead

of degrees. ISI fixes the problem immediately.



Timeline

Sept 9, 2015

After the modifications from the remote login of ISI to modify the tolerances in T&C MUS tool, the reconstruction and orbit determination process ran faster, however,

ISP 2926-3032 sec (expected: 3400 sec) Thrust 68-71 mN (expected 79 mN)

Cal (Ct.m) during the OD: .95 ot 1.5 ones

Therefore, losing the accuracy.

On-board RCN data were within expected values, so the OASYS-generated values must have been either incorrectly processed or inputs were incorrect. ABS requests ISI to look at the tolerances and see which LRVs should have tighter tolerances. After many tests and with ISI’s (Ryan) recommendation, TCT Tools’ tolerances were modified to get more data. LRV tolerances modified were:

40173/40175 (orifice temps) to 0.5 degC

32605/32705 (screen current) to 0.025 amps

32511/32512 (regulator pressure) to 0.25 kPa

Resulting to:

Thrust 80-82 mN

Isp 3400-3500 sec

However, the tolerances were too small that one maneuver had a thousand entries in ATD, resulting to around at least 5 hours of processing time in OASYS again.

After running more tests, the tolerances were modified again to reduce data in ATDs

40173/40175 (orifice temps) to 3.0 degC

32605/32705 (screen current) to 0.025 amps

32511/32512 (regulator pressure) to 0.25 kPa



Actual TLM versus the ATD File’s Values



Actual TLM versus the ATD File’s Values



Sample OASYS Output After Tolerance Modification



Timeline

Sept 11, 2015

Mom Dump Cmd Vector Change

Sept 14, 2015

Initial orbit state was provided by Boeing and new XPSDB file for planning was provided to replace the old file

Sept 16, 2015

Boeing Astrodynamics OJT ends.

ABS FD generated the tables to be uploaded. However, Boeing does not recommend that ABS uploads OASYS products due to the pending issue on momentum uncertainty. Upon the recommendation of Boeing Astrodynamics Team, the plans uploaded were generated by Boeing and its FDS.

Sept 23, 2015

ABS Uploads first tables generated by OASYS.

First maneuver table generated by the OASYS-generated products but without the Boeing-recommended momentum uncertainty



Timeline

Sept 27, 2015

After the first few days of OASYS-generated products (without momentum uncertainty)



Thruster Efficiency Thrust ISP

N1 1.00 80.93mN 3451.70sec

N2 0.92 81.24mN 3459.23sec

S1 0.93 80.73mN 3458.94sec

S2 0.98 80.85mN 3471.83sec

Orbital Parameters (OD)

EPOCH 27-Sept-2015 23:38:24.657

Semi Major Axis 42168.009 km

Eccentricity 0.000079.12

Inclination 0.029 deg

RAAN 192.926 deg

Arg of Perigee 157.578 deg

Mean Anomaly 7.530 deg

Additionally, the momentum was reduced to less than 1 Nms since implementing the

burn plan that was produced by OASYS (From ~2-5 Nms).

Momentum Management



Conclusion

At the time of submission of this presentation, ABS has performed 12 cycles of bi-weekly

uploads and has been successfully and efficiently managing the momentum and orbit of the

spacecraft. In addition, the database provides adjustment in parameters by which one can

increase or reduce the eccentricity control, delta in drift rate, etc, offering its users flexibility

in terms of planning. Therefore, ABS concludes that given the correct and compatible input

files to the software, OASYS v10.5.1b, using Boeing-provided libraries, is able to efficiently

perform Flight Dynamics processes for a 702SP satellite.



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