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ACE Payload Studies. Mark Schoeberl, Chuck McClain, Deborah Vane, Lisa Callahan, Richard Wessenberg, Armin Ellis. Goals of the Payload Study Group. Assess proposed payload options Feasibility Technical risk Foreign Partners Instrument maturity Cost Provide reports to NASA HQ

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Ace payload studies

ACE Payload Studies

Mark Schoeberl, Chuck McClain, Deborah Vane, Lisa Callahan, Richard Wessenberg, Armin Ellis

Goals of the payload study group
Goals of the Payload Study Group

  • Assess proposed payload options

    • Feasibility

    • Technical risk

    • Foreign Partners

    • Instrument maturity

    • Cost

  • Provide reports to NASA HQ

  • Mission will get go ahead when HQ is satisfied that we have a clear understanding of these elements and plans to move forward


  • A series of (JPL) Team X and GSFC (MDL) studies are scheduled for this spring.

    • JPL – Radar only platform (complete)

    • Ocean Ecosystem Spectrometer (OES) (April 6 IDL)

    • GSFC – Core (radar, lidar, polarimeter, OCR) (April 13, MDL)

    • GSFC – PACE (OES, 3MI, ATMS) (March 30, MDL)

    • JPL – Lidar, polarimeter (Date ?)

    • ??? – Radiometer+IR payload (date ?) Note the lack of radiometers or IR instruments on these platforms… this is an issue..

  • As part of these studies we are attempting to cost and assess TRL levels for various potential instrument components.

    • Cost assessment for some high TRL instruments are good

    • Low TRL instruments have uncertain costs

    • HQ will be looking for independent cost assessments (from RAO)

Trl levels just to review
TRL Levels – Just to Review

  • TRL 4: lab instrument - breadboard

  • TRL 5 aircraft instrument on DC-8 or equivalent

  • TRL 6: ER-2 instrument – in space like configuration

  • TRL 7: ready to launch

Trl of our favorite instruments
TRL of Our Favorite Instruments

My personal assessment….

We will need a lot of money and work to get these up to higher level. Currently HQ budget resources are directed at moving the Tier 1 missions to TRL 7.

Foreign partners
Foreign Partners

The issue here is who pursues these possible cost reducing partnerships. What are the implications for open competition? What about risk?

Mission design big missions vs little missions
Mission DesignBig Missions vs Little Missions

  • Small missions (e.g. CloudSat) are appealing because they are focused, have only 1-2 instruments and have simple systems engineering

    • However you need a bus and a rocket for each that means an overhead of $100-150M – even then they can be expensive (e.g. OCO)

    • Spacecraft has fewer resources so mission lifetime may be limited (e.g. Parasol)

  • Big missions are appealing because they have can give rides to many instruments and have more resources.

    • Need larger buses and larger rockets, but there is an economy of scale. Costs go up, however, if instrument delivery can’t be managed (NPP). System engineering is more complex, too.

  • ACE wants to fly many instruments. The right configuration is not obvious.

Ace configurations and timeline
ACE Configurations and Timeline

SWOT, HyspIRI, Ascends, ACE, GeoCAPE


Tier 1

Tier 2





OES, Polar

Lidar Polar.

Lidar Polar. OES

Lidar, Polar. OES, Radar









What is pace pre ace
What is PACE (Pre-ACE)?

  • EarthCare – one of the 6 ESA Earth Explorer satellites (LRD 2013) orbits at ~400 km, PSS, 13:45 crossing time

  • EC payload consists of

    • CPR 94 GHz, -36dBz Doppler radar

    • HSRL (355nm ) (ATLID)

    • Multi-angle BB IR Radiometer (2 channel, 0.2-4µ radiometer)

    • MSI - 7 channel, 150 km swath imager (500m nadir pixels, 0.66, 0.865, 1.6, 2.2, 8.2, 10.8, 12. µ)

  • EC lacks a polarimeter and a wide swath multi-channel UV-visible spectrometer ( like the OES)

  • PACE : fly NASA OES, CNES 3MI (Polder A) and ATMS behind EC to get early ACE-like data.

    • ATMS and 3MI are “free”.

    • WAG cost < $300M if CNES donates a bus.

  • ACE then launches the other instruments behind EC/PACE later in the decade – or we abandon the E-Train and launch to a higher orbit (450 km)

Notional ace pace observing geometry
Notional ACE+PACE : Observing Geometry

Orbit: 450 km SS following EC

Cloud Radar

Ocean Ecosystem Spectrometer







EarthCARE (2013)


HF (Green)

LF (Purple)


ACE A, B LRD 2020

HSR Lidar




Ocean Ecosystem Spectrometer

. The first unit is PACE - launches in 2015 with a polarimeter and the ocean biology spectrometer (OBS) and µ- wave nadir radiometer. PACE flies behind EarthCARE augmenting EC observations. The rest of ACE launches in ~2020. This configuration provides 8 years of measurements and continuity with EC. The PACE polarimeter and bus could be an international contribution.

Ace payload studies

3MI Multi-directional, Multi-angle, Multi-wavelength Imager

  • Type: Passive multi-angle imaging photopolarimeter

  • Instrument concept:Wide field of view telecentric optics (separate for VIS and SWIR), rotating wheel with spectral and polarization filters, and 2-D detector arrays in the focal plane of the optics

  • Directionality: 15 views of a scene, ±55° from nadir

  • Cross-track swath: ±55°

  • Approx. dimensions: 40 x 52 x 36 cm

  • Mass/power/data rate:30 kg / 30 W / 3 Mbps

  • Spectral range: 443–2130 nm

  • Measurement specifics: 2 visible (443, 490 nm), 2 near-IR (670, 865 nm), and 3 short-wave IR (1370, 1650, 2130 nm) bands; three Stokes parameters (I, Q, and U) in all channels except intensity-only channels 1 and 5. A UV band can be added. Polarization accuracy ~1%

  • Ground resolution at nadir: 2 km /4km

  • SNR requirement:200

  • Global coverage: 2 days

Ace payload studies

Filter wheel

VNIR optical head

SWIR optical head



FOV: 98°

FOV: 98°

Focal plane

Focal plane


Directional Polarisation Imager

Flight direction

  • 7 channels in VNIR + SWIR (5 polarised and 2 non-polarised)

  • 15 views of same point as spacecraft moves

  • Vicarious calibration

Filter wheel







Atms advanced technology wave sounder
ATMS Advanced Technology µ-wave Sounder

ATMS provides wide swath high spatial resolution microwave data to support temperature and humidity sounding generation in cloud covered conditions. In addition, ATMS provides advances in technology that allow the current operational temperature and moisture microwave sounder elements to be packaged in one sensor with less total weight, power, and volume

Ace and pace

PACE won’t be as good as ACE but we could get ACE-like measurements 5 years sooner.

  • The PACE HSRL is better than CALIPSO, the radar is better than CloudSat, the OES is better than MODIS (vis), the Polarimeter is better than Polder. PACE has a temperature/moisture sounder and thermal IR channels at the radar, lidar nadir points.

  • We will still need ACE, but because ACE is complicated, and expensive and has a lot of Low TRL instruments, it probably will not be the first out of the Tier 2 gate. Do we want data in 2015 or wait until 2020?

  • Do we try and fly parts of ACE after PACE, as soon as they are ready (e.g. the advanced radar)?

  • Will ACE die because of PACE? Very very very doubtful.

    • The argument that PACE can test some of the more advanced ACE technology ideas is cogent. EC/PACE gives us a good target for aircraft missions as part of the validation/instrument tests.

    • PACE gives us data to argue more strongly for ACE

    • ACE will be a much more powerful probe of Aerosol-Cloud Interaction and Cloud Processes than PACE interactions – its instruments are significant improvements

    • PACE will be contemporary with GPM

    • It is critical that PACE not delay ACE or be a substitute mission

    • If ACE and PACE can overlap – it makes ACE a 10 year mission

What still worries me about the payload
What still worries me about the payload…

  • We haven’t found an optimal payload configuration

  • We haven’t figured out how to engage foreign partners in an optimal way

  • We haven’t got a clear idea on how (or if) we are going to do the radiometers and the IR instrument

  • We have no temperature or moisture sounders (are we sure we don’t need those)

  • We are not working as a team and not speaking to in one voice to the outside world

Does the science team want pace
Does the Science Team want PACE?

  • We need a consensus to take to Mike F.