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D rag and A tmospheric N eutral D ensity E xplorer PowerPoint PPT Presentation


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D rag and A tmospheric N eutral D ensity E xplorer. Colorado Space Grant Consortium and CU Aerospace Engineering Sciences Meeting of the NADIR MURI October 21 st , 2008 Boulder, Colorado. DANDE - NADIR Seminar. Overview Introduction Science Instruments The DANDE Spacecraft

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D rag and a tmospheric n eutral d ensity e xplorer

Drag and Atmospheric NeutralDensity Explorer

Colorado Space Grant Consortium and CU Aerospace Engineering SciencesMeeting of the NADIR MURI

October 21st, 2008Boulder, Colorado


Dande nadir seminar

DANDE - NADIR Seminar

Overview

  • Introduction

  • Science

  • Instruments

  • The DANDE Spacecraft

  • Program Status


The university nanosat program

The University Nanosat Program

  • University Nanosat – The National Championships of Spacecraft Design

    • 2 year program in its fifth iteration

    • 10 out of 30 university proposals selected based on Air Force Relevance

    • $85k initial seed funding for hardware and student support

    • In January 2009, one school wins additional $85k, I&T at Kirtland, and flight to Orbit

  • CU Nanosat Entry

    • Has involved a core team of graduate students and expanded into 40 graduate and undergraduate students

    • Many aspects of the ASEN Graduate Projects but organized as independent research and MS research

    • Has leveraged over $240k from University, Department, DoD, and COSGC Funds

I - Introduction


Nanosat v program at cu

Nanosat V Program at CU

DANDE will improve atmospheric models and calibrate near real-time models by measuring the following

  • Deceleration

  • Atmospheric composition

  • Horizontal Winds

    DANDE is spherically shaped to minimize biases resulting from estimation of the drag coefficient

I - Introduction


Dande nadir synergies

DANDE – NADIR Synergies

  • Provide the information to improve empirical models of neutral density

  • Determine the relationship between neutral density structure and satellite drag

  • Understand the physical processes driving the variability of neutral atmospheric density

I - Objectives and Requirements


Background and motivation

Relative Orbit of Two Separating Spacecraft

drag induced drift

Background and Motivation

Storm response of CHAMP E/W winds

Scientific understanding hindered by lack of neutral density, composition, and wind measurements

Precise orbit prediction depends on accurate knowledge of atmospheric density and in particular excursions from the mean state

I - Introduction


Dande science

DANDE Science

7


Mission statement

Mission Statement

DRAG and ATMOSPHERIC NEUTRAL DENSITY EXPLORER

Mission Statement

Explore the spatial and temporal variability of the neutral thermosphere at altitudes of 350 - 200 km, and investigate how wind and density variability translate to drag forces on satellites.

II - DANDE Science


Objectives and compelling science questions addressed by dande

Objectives and Compelling Science Questions Addressed by DANDE

II - DANDE Science


Objective requirements

Objective Requirements

Measure in-situ density and composition (O:N2 ratio) during at least 5 sudden geomagnetic storms and 4 periods of quiet geomagnetic conditions in an altitude of at most 350 km and covering a minimum latitude of at least 54 degrees

Calibration and validation of models. Goal: also estimate the coefficient of drag in orbit at 350 - 100 km altitude.

Measure neutral winds at an altitude of up to 250 km and below and at latitudes of at least 54 degrees during 5 sudden geomagnetic storms and 4 periods of quiet geomagnetic conditions. Provide the wind data with a spatial resolution of at least 500 km (goal: 100 km).

Measure large-scale horizontal variations with in-situ density data over the course of at least 5 geomagnetic storms and 4 periods of quiet geomagnetic conditions

Develop a low-cost system to make in-situ measurements of the neutral atmosphere and adhere to Nanosat Program Requirements. Finish the proto-qualification unit on time and on budget.

II - DANDE Science


Minimum measurement requirements

Minimum Measurement Requirements

horizontal resolution of 500km (~64s)

1.SYS26 , composition measurements with resolution of 1.5 m/Δm. Driven by 0.SYS1 and 1.SYS21

(where m/Δm = half peak width at mass m)

*percent value based on average conditions during solar maximum, vernal equinox

**assuming a wind velocity of 1 km/s, storm conditions

II - DANDE Science


Wind and density requirement relationship

Goal

Requirement

Wind and Density Requirement Relationship

II - DANDE Science


How measurements are made

How Measurements are Made

Identifying all components of the constituents of the drag equation.

With a near-spherical shape, an a-priori physical drag coefficient may be calculated and a physical density can be obtained from the measurements

A

atmosphere

ρ - density

VW

FD

V

CD

tracking

WTS sensor

accelerometers

solution

a priori knowledge

a priori knowledge

a priori knowledge/ comparison

solved

II - DANDE Science

13


Dande science instruments

DANDE Science Instruments

14


Accelerometers

QA-2000 accelerometer

x 6

Cost~$3,000

Precisionng*

Bandwidth 6 μHz – 10 KHz**

**must be able to reject the larger noise outside of 6 μHz - 1 Hz to achieve

79 ng

Accelerometers

STAR accelerometer

Method to reduce this drift

  • Flip one accelerometer in positive and negative directions and remove bias

  • Modulate measurement to 6 μHz - 1 Hzrange

  • 6 reduces the noise through averaging independent measurements by 0.41 (1/√6)

  • Provides redundancy

Cost~$3,000,000

Precision30 ng

Bandwidth10mHz – 100mHz

III - DANDE Science Instruments


Accelerometer measurement system

Low frequency bias

spin rate

ANALOG FILTERING

A/D CONVERSION

LEAST SQUARES

70 ng

Accelerometer Measurement System

III - DANDE Science Instruments


Problem description measurement system

Problem Description: Measurement System

ACC-2

ACC-4

ACC-1

ACC-6

ACC-3

ω

ACC-5

R

T

ACC-2

FD

ACC-1

ACC-3

ω = π/3 [rad/sec]

ACC-4

PROCESS &

AVERAGE

ACC-5

ACC-6

III - DANDE Science Instruments


Accelerometer analysis

82∘

82∘

82∘

-82∘

-82∘

-82∘

0∘

0∘

0∘

0∘

0∘

0∘

82∘

-82∘

0∘

0∘

Accelerometer Analysis

Latitude [deg]

III - DANDE Science Instruments


Wind and temperature spectrometer

Wind and Temperature Spectrometer

Incoming Neutrals

III - DANDE Science Instruments

19


Wind and temperature spectrometer1

Wind and Temperature Spectrometer

  • Neutral particle (blue) enters the collimator. (Ions rejected)

  • Neutral particle is ionized inside of a field free electron bombardment region

  • Neutral particle enters the energy selector and undergoes acceleration towards the exit

  • Outside the selector, the particle is accelerated abruptly by a -3kV potential towards the Micro-Channel Plate (MCP)

  • The impact on the MCP causes a cascade of electrons to travel towards one of the anodes which measures the impact. Which anode is triggered depends on the angle at which the neutral particle entered the collimator.

III - DANDE Science Instruments

20


Wind and temperature spectrometer2

Wind and Temperature Spectrometer

Peak count of vertical distribution

~2000 counts

ACC-2

ACC-4

ACC-1

ACC-6

ACC-3

ω

ACC-5

# of particles impacting detector

R

T

Angular position about the satellite spin axis, degrees

Total number densities across all spectra as the satellite spins

W

III - DANDE Science Instruments

21


Wts science data product analysis

WTS Science Data Product Analysis

wind angle

O wind mag.

N2temp.

O temp.

N2 wind mag.

III - DANDE Science Instruments

22


Wind and temperature spectrometer3

Wind and Temperature Spectrometer

Will meet science requirements and goals

  • The error depends on the number of particles registered.

  • Determined for a true wind velocity magnitude W of 10 m/s:

DANDE

*from Herrero et. al. unpublished work

III - DANDE Science Instruments

23


Wind and density requirement relationship1

Design

Wind and Density Requirement Relationship

III - DANDE Science Instruments


Density error drag and wind data

Density Error – Drag and Wind Data

III - DANDE Science Instruments


Complex geometry effects

Complex Geometry Effects

A behavior different from that of smooth spheres is observed for the faceted spheres. What is the physical drag coefficient of a faceted surface?

Physical CDP, partly quasi-specular

Physical CDP, 100% diffuse

Fitted CD

Expected fit

Starshine I

[Bowman & Moe 2005]

III - DANDE Science Instruments


Results impacts on starshine surface

Results: Impacts on Starshine Surface

Percentage of Total Impacts

0.06 %

“latitude”

0.01 %

“longitude”

2∘ x 2∘ bins

III - DANDE Science Instruments


Drag coefficient of dande

Drag Coefficient of DANDE

Bias induced by CD uncertainty using method of [Moe and Moe, 1996] at solar max

(2.216 - 2.118)/2.216 = 4.5%

III - DANDE Science Instruments


Spacecraft engineering

Spacecraft Engineering

29


Dande overview

Baseline Configuration

ESPA Ring

DANDE Sphere

18”

Lightband Adapter Bracket (LAB)

DANDE Overview

IV - Spacecraft Engineering


D rag and a tmospheric n eutral d ensity e xplorer

Day 2

Day 1

LV SEPARATION AND COMMISSIONING PHASE

Wind

Composition

Acceleration

Tracking

Tracking

Day 9

Day 100

DATA ACQUISITION

1 orbit SCIENCE

1 orbit STANDBY

DOWNLINK/UPLINK

~2x in 24 hours

ATTITUDE ADJUST

~1 orbit per day

RE-ENTRY DYNAMICS

~LAST WEEK OF ORBIT

200 km – 100 km

SCIENCE PHASE

Mission Timeline

  • Phase 1: LV Separation and commissioning

    • Launch Mode - time delay – Safe Mode

    • Full charge and checkout[18 – 30 hours]

    • Lightband jettison

  • Phase 2: Attitude Acquisition

    • Spin Up [24 h]

    • Spin-Axis Alignment [120h]

    • Reserve time [24h]

  • Phase 3: Science [~90 days]

    • Science Mode

    • Standby Mode

    • Comm. Pass

    • Attitude Adjust

    • Repeat

IV - Spacecraft Engineering

31


Spacecraft layout

Spacecraft Layout

IV - Spacecraft Engineering


D rag and a tmospheric n eutral d ensity e xplorer

DANDE Attitude

  • Spin stabilization about orbit normal

    • 40°/sec (10 rpm)

    • Only two maneuvers: spin-up and axis alignment

  • Sensors

    • Magnetometer for spin-up

    • Horizon Crossing Indicators for spin axis alignment

  • Actuators

    • 2x Torque rods: one along spin axis and one transverse

    • Passive nutation damper

IV - Spacecraft Engineering

33


Program status

Program Status

34


Completed formal testing

Completed Formal Testing

TESTING

V - Program Status


State of the dande program hardware

State of the DANDE Program: Hardware

HARDWARE & MANUFACTURING

Lessons

Learned

Engineering Design Unit

Competition Review Hardware

V - Program Status


Integration testing schedule

Integration & Testing Schedule

Today

Competition Review

V - Program Status


Questions

Questions

dande.colorado.edu


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