5.625 Gbps Bidirectional Laser Communications Measurements Between the NFIRE Satellite and an Optical Ground Station Mark Gregorya, Bernhard Wandernotha, David Kozlowskib, Harold Yurab, Frank Heinea, Andreas Paapec , Rolf Meyerd, Robert Wongb, Josef Wickerb, Carl Lundeb, and Renny Fieldsb a

Tesat-Spacecom, Gerberstrasse 49, Backnang, Germany, bThe Aerospace Corporation, 2350 E. El Segundo Blvd.,El Segundo, California 90245, cGerman Liaison Office for Defense Material, 11150 Sunrise Valley Drive, Reston,Virgina 20191 d DLR-German Aerospace Center, Koenigswintererstrasse 522-524, Bonn, Germany

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Approved for Public Release 11-MDA-5958 (17 FEB 11)

Duplex Ground-to-Space Lasercom Outline • • • •

•

Introduction to NFIRE lasercom and the project origin Context of this activity Crosslinks and Maui groundlinks Results at Tenerife – Comm link results – Comparison of previous atmospheric analysis vs our estimates – Pointing Summary The support of the German Federal Office of Defense Technology and Procurement and the Missile Defense Agency as administered through the U.S. Air Force Space and Missile Systems Center under Contract No. FA8802-09-C-0001 is greatly acknowledged.

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Joint Laser Comm Project Introduction to NFIRE NFIRE Launch April 24, 2007

• •

Near Field InfraRed Experiment Primary experiment to gather Visible and IR images at close range from boosting target

LCT TSP Key Features

PCA: 237s ~ 3 km

• Short/Mid-Wave IR, Long Wave IR and Visible Cameras

Tracking

• Track targets on any of the three cameras

Reacquisition

NFIRE Final Configuration With LCT:2006

• Satellite-fixed, Earthfixed and inertial pointing modes • Reacquisition mode using target position from SC

Tracking

Track Sensor Payload

Earth Fixed Stare

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Primary Payload Deleted & Program Restart Dec 2004

Many Space-to-Space accomplishments TerraSAR-X Launch June 15, 2007

NFIRE

TerraSAR-X

• • • • •

Mean open loop acquisition error of 140 micro-radians – Spatial acquisition in several seconds Links > 600 seconds with no bit errors Currently in reliability testing, near 100% reliability when known component issues are factored into results Over 100 links performed No noticeable in-orbit disturbances on links

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Date

4

12/31

12/24

12/17

12/10

12/3

11/26

11/19

11/12

0 10/1

– , 48° degree elevation

5 11/5

NFIRE: Elliptical orbit is 450 circular

10

10/29

– 495 km Altitude, 98° Inclination

15

10/22

TerraSAR-X: Sun synchronous orbit

20

10/15

Satellite Orbit Characteristics

10/8

Minutes per contact

NFIRE – TerraSAR-X Comm Interval Duration vs. Date

Hardware and some engagement details Ø 12.5 cm

LCT Key Features

• • • • • • •

Ø 6.5 cm

32 kg, 125 watts power consumption 57 cm corner-to-corner terminal foot print 1553 TM/TC Interface 5.625 Gbs full duplex data rate 1.5 W Max Transmitted Power @ 1.064 m 10 mrad Field of View Hemispherical Pointing Capability Ground version of LCT in Tenerife

Space version of LCT on NFIRE

Satellite Orbit Characteristics 24

Pump Module

Ch 0

TX Laser Head

EO Modulator

LO Laser Head

RX

Bi-Directional: BPSK, Homodyne, 1064 nm

Optical Power Amp

Coherent RX

24 Ch 0

To

From

NFIRE: Elliptical orbit opportunities – 440 by 360 km Altitude, 48° degree inclination

Telescope & Gimbal

TX

TX Data Electronics

RX Data Electronics

Data Electronics: 5.625 GBits/s Full Data Rate 24 Data Channels Ch 0 Optical Service Channel, Link Optimization, POT, PAA, POS Channels Scram. and Mux, Differential Encoding [email protected] Missile Defense Space Systems [email protected] Electronics and Photonics Laboratory

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Lasercom from Maui was challenging • • • •

At 3058 m, Haleakala should have posed no issue wrt r0 and the 6.5 cm aperture High Winds and an exposed terminal contributed to many track losses No success during the day and large mean deviation for r0 across test days Maui3 model for Cn2 profile suggested r0 and SI were fine

Statistic Total number of planned SGLs

50

Total number performed

40

Total number not performed because of Weather, Scheduling, Hardware, NFIRE-LCT problem

10

Tracking

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Maui 2009 Campaign

31.6%

Uplink communication only

0

Downlink communication only

5

Bi-directional communication

0

6

Move to Tenerife • • • •

OGS Tenerife at 2400 m, Volcanic Island in Atlantic Ocean LCT mounted in a Dome Once over bad weather conditions Jan - April, links were successful Maui3 model for Cn2 profile fit data well Sahara Dust

Statistic Total number of planned SGLs

Wind, Rain, Fog and Clouds Snow and Ice

126

Total number performed

79

Total number not performed because of Weather, Scheduling, Hardware, NFIRE-LCT problem

47

Tracking

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Tenerife 2010 Campaign

79.0%

Uplink communication only

8

Downlink communication only

1

Bi-directional communication

9

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Table of all SGL executed in Tenerife 2010

Green shading indicates links which resulted in Communication link success (bidirectional and one-way)

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62.493 40.048 87.625 28.115 44.694 58.46 20.17 67.07 38.71 34.41 81.46 49.75 30.113 73.253 48.54 45.37 78.91 29.42 68.863 61.587 35.999 30.828 74.822 48.292 42.545 83.946 26.728 32.558 30.164 71.136 53.712 48.964 40.478 24.428 46.258 48.96 61.603 36.103 80.227 83.741 48.251

27 Apr 2010 09:24:40.845 28 Apr 2010 08:23:27.043 30 Apr 2010 07:56:35.759 01 May 2010 06:55:29.544 02 May 2010 07:29:52.177 03 May 2010 06:28:19.623 04 May 2010 05:27:13.024 05 May 2010 06:01:06.601 06 May 2010 04:59:39.829 07 May 2010 05:34:07.611 08 May 2010 04:32:16.102 10 May 2010 04:04:59.765 15 May 2010 10:15:17.314 16 May 2010 01:07:05.084 18 May 2010 08:44:51.223 18 May 2010 23:36:51.388 21 May 2010 07:14:55.683 21 May 2010 22:07:13.481 25 May 2010 21:10:30.410 26 May 2010 05:16:24.255 26 May 2010 20:08:38.049 28 May 2010 04:48:18.897 28 May 2010 19:40:13.322 12 Jun 2010 21:49:33.058 13 Jun 2010 12:41:52.739 15 Jun 2010 12:14:12.585 16 Jun 2010 11:12:12.918 21 Jun 2010 09:12:10.692 22 Jun 2010 17:51:18.033 23 Jun 2010 08:43:19.655 25 Jun 2010 08:14:26.378 25 Jun 2010 16:19:54.196 26 Jun 2010 07:12:03.462 29 Jun 2010 05:39:52.036 30 Jun 2010 06:12:55.670 08 Jul 2010 02:13:54.426 08 Jul 2010 10:23:10.922 10 Jul 2010 10:16:00.968 11 Jul 2010 01:14:33.584 11 Jul 2010 09:23:53.699 14 Jul 2010 08:26:52.712

D D D D D D N D N N N N D D D N D N N N N N D N D D D D D D D D D N N N D D N D D

59.236

14 Jul 2010 23:25:39.640

N

26.31 38.015

15 Jul 2010 22:34:10.981 16 Jul 2010 23:18:48.024

N D

30.233

17 Jul 2010 07:28:12.168

D

41.857 68.545

21 Jul 2010 05:37:11.769 21 Jul 2010 20:35:54.546

N N

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Lock to IF at OGS, NFIRE Communication for 69s Sahara dust First Time Bi‐di Comm for 6s, NFIRE comms for 32s Clouds, only 28deg elevation No signal received from NFIRE Communication on NFIRE for 44s 20  degree rlevation pass and thin cloud layer Bi‐di Comm for 6.9s, 86.9s of uplink comms on NFIRE Bad signal quality, Pass into wind direction Problem with  dome software, SGL terminated early Bad weather, high clouds Bi‐di Comm for 15s, Range NFIRE and OGS measured Limited output power OGS Bad tracking quality due to haze Bad signal quality Bad signal quality Bi‐di Comm 30s, Range  NFIRE and OGS measured Some fog No Signal on camera and Sensors Weak CAS and FAS hits. Too low for stable FAS tracking No CAS but camera in beginning No transition to tracking, bad CAS hit at transition Tracking with interruptions, no comms on ground Communication on NFIRE for 98.6s Communication on NFIRE for 58.1s  No signal on camera and Sensors Low elevation pass (27deg) Cancelled by LCH No communication Bi‐di Comm for 67.8s, 72.4s comms at OGS Many tracking interuptions 21s lock at OGS to IF  No lock OGS, NFIRE comms for 120.2s wit interrhupt OGS Lock to IF, no NFIRE Comms Many tracking interuptions Bidi communication for 15.5s Bidi communication for 6.1s Bad signal quality, sahara dust No Comm, many interrupts, IF Lock OGS, NFIRE Lock 57s Bidi comm for 45.8s with  interrupts Low elevation, short tracking Bidi comm 177s, Range data full pass, Humidity 30 %, wind speed 3  km/hr ~ 1 m/s, Temp 17 C Low elevation, OGS IF Lock, NFIRE no lock, Humidity 50%, wind 12 km/hr 3.3 m/s, Temp 15 C IF Lock OGS , NFIRE Comms for 182s, short interrupts Humidity 25%, Wind 18 km/hr , 16 C, short coherent tracking, no comm  NFIRE, high res meas NFIRE High winds 36 km/hr , R0 of  6cm measured by Aerospace, high res meas  NFIRE, 30 % Humidity,  IF Lock OGS, NFIRE comm for 125s, range measured

Turbulence Models for Tenerife

Predicted and Measured, SI and r0 at 500 nm and Zenith

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Scintillation Index, SI

SI, with Nfire and OGS aperture averaging

r0, cm

Model

0.11

0.0085 (500 nm extrap))

12.9 cm

Maui3

0.01 (500 nm)

13 cm

Measured at OGS July 2010

0.107

6.5 cm

Spanish-Night

0.191

4.4 cm

Spanish-Day-1

1.8 cm

Spanish-Day-2

0.211 9

Vizualisation of the SGL on the 14th of July 2010

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HR FAS signal and Mission Characteristics TOP: Bottom:

High Resolution FAS signal with time Range and Elevation with time

Envelope of FAS signal intensity fluctuations, due to atmospheric scintillation, traces an Hour-Glass shape indicative of the elevation trajectory from low-maxima-low Pockets of increased fluctuations can be seen The dropout in the middle is due to an obscuration inside the dome at the apex of the elevation angle Note: both NFIRE and the ground LCT remained/regained lock through the fade.

Constant Power on Target As with all the SGLs, the range varied over the engagement, however a propagator range dependent power adjustment routine on both LCTs was active (as always) to ensure constant power at each terminal. Therefore, any power fluctuations are due solely to atmospheric effects

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Scintillation Index dependence on elevation Measured FAS (1064 nm) SI Direct-detection plotted versus elevation angle Three regions are highlighted i) Ascending elevation prior to Coherent Lock ii) Ascending elevation while in bidirectional comm iii) Descending elevation whilst in bidirectional comm Blue continuous line is predicted SI with elevation using the Maui3 Model and includes NFIRE Tx and OGS Rx aperture averaging

Measured FAS (1064 nm) SI Direct-detection measurement Normalized to 500 nm and Zenith Regions of Ascending and Descending elevation are noted Pockets of Increased SI are obvious and are indicated Background level ~ 0.015 to 0.02

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FFT and STFT of FAS signal

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r0 July 2010 on La Palma Night-time r0 is routinely measured by ING on La Palma La Palma is 120 km from Tenerife Daily weather conditions on La Palma are similar to Tenerife Climatically and Atmospherically Tenerife is similar to La Palma

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Comparing Seeing: Tenerife with La Palma

Our measurements at the OGS on Tenerife

ING measurements on La Palma

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Ground site differences between Maui and Tenerife

ESA OGS to:

• • • •

IAC-80 VTT Rock WNW Teide

171.919 m 236.209 m 2430.056 m 12,983.731 m

A major issue for a ground site is to have retro-mirror sites that are sufficiently distant and can be accurately measured to determine the ECI attitude of the ground position Maui was very challenging due to the position of the Ground LCT and landmarks were viewable Significant RF noise on Haleakala impacted accuracy of GPS retro determinations Eventually resolved by making NFIRE the master and then using subsequent links to correct the Ground LCT attitude

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16

Pointing

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Conclusions, Future Work and Acknowledgements •

Conclusions – 1st repeated giga-bit class LEO to Ground bidirectional laser communication link – Tenerife atmospheric conditions are statistically well represented by the Maui3 profile – Consistent high data rate SI measurements were made over a wide range of elevation

•

Future Work – Open loop pointing errors over many links indicate that a better bias offset for the Gimbal on NFIRE’s LCT could significantly improve open loop pointing for all engagements – Intend to move down in ground station altitude and optimize independent atmospheric measurements on the 1 micron NFIRE signal

• Acknowledgements – – – –

OGS under ESA as administered by Zoran Sodnik The Institute of Astrophysics at the Canaries Issac Newton Group (ING) at La Palma Donald Walters

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