# PART 3 - TECHNOLOGY VALIDATION

# 2. SPACECRAFT BUS TECHNOLOGY OVERVIEW

## 2.1 Introduction

The following seven crosscutting technologies, which will reduce the
cost, mass and complexity of future Earth observing spacecraft and allow
more scientific payload to fly on future missions, were demonstrated by
EO-1:

1.  X-Band Phased Array Antenna (XPAA)

2.  Wideband Advanced Recorder Processor (WARP)

3.  Enhanced Formation Flying (EFF)

4.  Pulsed Plasma Thruster (PPT)

5.  Lightweight Flexible Solar Array (LFSA)

6.  Carbon-Carbon Radiator (CCR)

7.  LA-II Thermal Coating

## 2.2 X-Band Phased Array Antenna (XPAA)

![](media/image1.jpeg){width="2.175in" height="1.63125in"}The New
Millennium Program\'s Earth Observing-1 (EO-1) mission provides for the
on-orbit demonstration of a high data rate, low mass X-Band Phased Array
Antenna (XPAA) for down-linking imaged data from the EO-1 solid state
recorder. The XPAA offers significant benefits over current mechanically
pointed parabolic antennas, including the elimination of deployable
structures, moving parts, and the torque disturbances that moving
antennas impart to the spacecraft.

The XPAA is composed of a flat grid of 64 radiating elements whose
transmitted signals are combined spatially to produce the desired
antenna directivity. The phases of each of the radiating elements are
varied by computer to point the beam in the desired direction. For the
EO-1 mission, the radiating elements are combined with low power, high
efficiency solid-state amplifiers to achieve the required radio
frequency power level. The antenna is mounted on the Earth-facing side
of the spacecraft to allow communications with ground stations. The
antenna\'s mass is 5.5 kilograms and is contained in a single 12 x 13 x
2.9 inch enclosure. It has a minimum Effective Isotropic Radiated Power
(EIRP) of 22 dBW and transmits data at 105 megabits per second.

## 2.3 Wideband Advanced Recorder and Processor (WARP)

![](media/image2.png){width="1.6680555555555556in"
height="2.152083333333333in"}The Wideband Advanced Recorder and
Processor (WARP) is a high rate solid-state recorder on EO-1 used to
capture a range of high rate data from the Advanced Land Imager (ALI),
Hyperion, and the LEISA Atmospheric Corrector (AC) instruments. The
combined continuous data rate from these three instruments is about 500
Mbps. When commanded, the instruments acquire ground images and transfer
those scenes at high rates to the WARP. The WARP stores the scenes as
files in bulk memory. When in contact with a ground station, the WARP
automatically transmits the scenes via an X-band downlink or an S-band
backup downlink.

The WARP consists of a high record rate (up to 900 Mbps continuous
capability), high density storage(48 Gbits), and low mass (18 kg)
solid-state recorder/processor with 105 Mbps X-band modulation playback
capability. It uses advanced integrated circuit packaging (3D stacked
memory devices) and \"chip on board\" wire bonding techniques to obtain
extremely high-density memory storage per board (24Gbits/memory card).
The Processor Board contains a 32 bit microprocessor called a Mongoose 5
that, in addition to performing basic data record and playback
functions, has the additional capability of post-processing science
data. However, this additional capability was never developed due to
schedule constraints. Examples of post-processing functions that were
originally intended include thumbnail imaging, cloud detection, and data
compression.

## 2.4 Enhanced Formation Flying (EFF) - NASA Goddard Space Flight Center and Jet Propulsion Laboratory

![](media/image3.png){width="2.05in"
height="1.7361111111111112in"}Enhanced formation flying (EFF)
technology, for onboard autonomous constellation and formation flying
control, will enable a large number of spacecraft to be managed with a
minimum of ground support. The result will be a group of spacecraft with
the ability to detect errors and cooperatively agree on the appropriate
maneuver to maintain their desired positions and orientations. The EFF
technology is applicable to any mission class, be it low-Earth or Deep
Space, that desires to fly multiple satellites autonomously while
gaining the added benefit of enabling science and reducing mission
operations costs.

The EO-1 EFF technology features flight software that is capable of
autonomously planning, executing, and calibrating routine spacecraft
maneuvers to maintain satellites in their respective constellations and
formations. The EO-1 mission formation flying requirement is that the
spacecraft fly only 1 minute (450 km) behind Landsat 7 in the same
ground track and maintain the separation within 2 seconds. This close
separation enables EO-1 to observe the same ground scene through the
same atmospheric region so that paired scene comparisons can be made.

Unique features of the EFF technology include an innovative use of fuzzy
logic decision making capabilities and natural language scripting to
resolve multiple conflicting constraints and to enable algorithm updates
without software changes; flight wrapper that interfaces directly with
the command and data handling subsystem for input and output; multiple
operating modes to allow execution control; generic closed-loop
formation flying control algorithms that are applicable to many
missions; and a modular architecture design that is flexible enough to
control execution of multiple and varying algorithms from several
partners.

## 2.5 Pulsed Plasma Thruster (PPT)

The New Millennium Program\'s Earth Observing-1 (EO-1) mission provides
for the first on-orbit demonstration of a low mass, low cost, dependable
electromagnetic Pulse Plasma Thruster (PPT) propulsion unit designed for
precision attitude control. The PPT uses solid Teflon propellant and is
capable of delivering high specific impulse (650 - 1400 sec), very fine
impulse bits (90 -- 860 µN-s) at low power (12 -- 70 W), and an
estimated total impulse of 460 N-sec. The total mass is \~5 kg.

![](media/image4.wmf){width="2.0in" height="1.5930555555555554in"}

The PPT consists of a coiled spring to feed the Teflon propellant, an
igniter plug to initiate a small trigger discharge and an energy storage
capacitor and electrodes. Plasma is created by the ablation of the
Teflon propellant from discharge of the storage capacitor across the
electrodes. The plasma is accelerated by Lorenz force in the induced
magnetic field to generate thrust. The thrust is modulated by varying
the magnitude of the impulse bit. The impulse bit is varied by changing
the charge time of the main capacitor. When commanded, the PPT replaces
the function of the pitch axis reaction wheel and maintains fine pitch
attitude control pointing requirements for EO-1 while meeting stringent
electromagnetic and contamination constraints for the mission.

## 2.6 Lightweight Flexible Solar Array (LFSA)

The Light Weight Flexible Solar Array (LFSA) is a lightweight
photovoltaic solar array system. The unique new technology features of
the LFSA are the use of copper indium diselinide (CulnSe2 or CIS) solar
cells on a flexible substrate and use of shape memory alloys (SMA) for
the hinge and deployment system. Each of two panels is approximately 5
in. wide by 18 in. long. The LFSA is deployed by heating the SMA hinges.
Photographs of the deployed LFSA assembly and a SMA hinge are shown
below.

  ------------------------------------- -----------------------------------------
  ![](media/image5.wmf)                 ![](media/image6.wmf){width="1.89375in"
                                        height="1.5715277777777779in"}

  ------------------------------------- -----------------------------------------

Combination of the CIS solar cell, flexible substrate, and SMA
technologies can provide significant improvement in power to weight
ratios. In addition, the SMA provides a shockless deployment environment
that can mitigate adverse spacecraft dynamics effects during deployment
and is also much safer than conventional solar array systems using
conventional pyrotechnics for deployment. The goal of the LFSA
technology is to achieve greater than 175 Watts/kg power efficiency
ratios compared to conventional solar arrays that provide less than 40
Watts/kg.

## 2.7 Carbon-Carbon Radiator (CCR)

Carbon-Carbon is a special composite material that uses pure carbon for
both the fiber and matrix. The advantages of Carbon-Carbon are that it
possesses high thermal conductivity, including through thickness, and
has strength to weight characteristics superior to aluminum. The
Carbon-Carbon Radiator (CCR) panel is 28.62 in. x 28.25 in. in size. It
is a sandwich panel that consists of two 0.022-in.-thick C-C facesheets
bonded to a 1-in. 5056 aluminum honeycomb core. The internal surface of
the CCR panel is coated with an epoxy encapsulate to prevent particle
contamination of sensitive instruments on board EO-1 and provide
additional strength to the panel. The external surface of the panel is
coated with silver Teflon as required by the EO-1 spacecraft thermal
design. Photographs of the flight panel are shown below.

![](media/image7.wmf){width="5.438194444444444in" height="1.90625in"}

The primary thermal function of the EO-1 CCR is to radiate the 27.8
watts generated by the EO-1 Power Supply Electronics (PSE) and the 16.3
watts (peak power) generated by Linear Etalon Imaging Spectral
Array/Atmospheric Corrector (LEISA/AC) electronics boxes. The panel also
serves as a primary structural member and is required to support the
combined weight of the PSE (50 lb) and the LAC (10 lb) boxes while being
subjected to severe mechanical launch environmental loading conditions.
Therefore, the objective of this technology validation is to demonstrate
that Carbon-Carbon can be a cost efficient facesheet material for
honeycomb core radiator panels that also function as part of the
spacecraft primary structure.

## 2.8 LA-II Thermal Coating

![](media/image8.wmf){width="2.1458333333333335in"
height="1.7291666666666667in"}The LA-II thermal coating is a low
absorptance inorganic white paint. The purpose of this technology
demonstration is to validate the thermal performance of an improved
white thermal control coating developed by AZ Technology, Inc. A low
absorptance thermal coating will allow radiators to run cooler when
exposed to a UV environment and thereby provide improved performance for
space radiators. The known NASA/GSFC Z93P White Paint was used as a
baseline thermal coating for comparison purposes.

Two flight calorimeters, as shown to the right, were mounted on a common
aluminum bracket that was attached to the EO-1 equipment bay panel. The
calorimeters contained disc samples of the two thermal coating paints.
In addition to providing a structural mount to the spacecraft, the
bracket allows the disc samples to reside above the radiator surface,
thereby increasing the view factor to space and reducing inputs from
other spacecraft components.