+---------+---+---+---+------------+------+----------+---+---------------+
| ![]     |   |   | [ |            |      |          |   | NRA-02-OES-06 |
| (media/ |   |   | P |            |      |          |   |               |
| image1. |   |   | r |            |      |          |   | Proposal      |
| jpeg){w |   |   | o |            |      |          |   | Number:       |
| idth="0 |   |   | p |            |      |          |   |               |
| .675in" |   |   | o |            |      |          |   | (Leave blank  |
| he      |   |   | s |            |      |          |   | for NASA use) |
| ight="0 |   |   | a |            |      |          |   |               |
| .582638 |   |   | l |            |      |          |   |               |
| 8888888 |   |   | C |            |      |          |   |               |
| 889in"} |   |   | o |            |      |          |   |               |
|         |   |   | v |            |      |          |   |               |
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|         |   |   | ] |            |      |          |   |               |
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|         |   |   | : |            |      |          |   |               |
|         |   |   | 1 |            |      |          |   |               |
|         |   |   | 2 |            |      |          |   |               |
|         |   |   | / |            |      |          |   |               |
|         |   |   | 9 |            |      |          |   |               |
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|         |   |   | 2 |            |      |          |   |               |
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|         |   |   | 0 |            |      |          |   |               |
|         |   |   | 2 |            |      |          |   |               |
+---------+---+---+---+------------+------+----------+---+---------------+
| Name of |   |   |   | NASA Ames  |      | **Congr  |   | California    |
| Sub     |   |   |   | Research   |      | essional |   | #14           |
| mitting |   |   |   | Center     |      | Dis      |   |               |
| Insti   |   |   |   |            |      | trict:** |   |               |
| tution: |   |   |   |            |      |          |   |               |
+---------+---+---+---+------------+------+----------+---+---------------+
| **P     | D |   |   |            |      |          |   |               |
| roposal | e |   |   |            |      |          |   |               |
| T       | v |   |   |            |      |          |   |               |
| itle:** | e |   |   |            |      |          |   |               |
|         | l |   |   |            |      |          |   |               |
|         | o |   |   |            |      |          |   |               |
|         | p |   |   |            |      |          |   |               |
|         | m |   |   |            |      |          |   |               |
|         | e |   |   |            |      |          |   |               |
|         | n |   |   |            |      |          |   |               |
|         | t |   |   |            |      |          |   |               |
|         | o |   |   |            |      |          |   |               |
|         | f |   |   |            |      |          |   |               |
|         | a |   |   |            |      |          |   |               |
|         | n |   |   |            |      |          |   |               |
|         | A |   |   |            |      |          |   |               |
|         | i |   |   |            |      |          |   |               |
|         | r |   |   |            |      |          |   |               |
|         | b |   |   |            |      |          |   |               |
|         | o |   |   |            |      |          |   |               |
|         | r |   |   |            |      |          |   |               |
|         | n |   |   |            |      |          |   |               |
|         | e |   |   |            |      |          |   |               |
|         | S |   |   |            |      |          |   |               |
|         | u |   |   |            |      |          |   |               |
|         | n |   |   |            |      |          |   |               |
|         | - |   |   |            |      |          |   |               |
|         | s |   |   |            |      |          |   |               |
|         | k |   |   |            |      |          |   |               |
|         | y |   |   |            |      |          |   |               |
|         | A |   |   |            |      |          |   |               |
|         | u |   |   |            |      |          |   |               |
|         | t |   |   |            |      |          |   |               |
|         | o |   |   |            |      |          |   |               |
|         | - |   |   |            |      |          |   |               |
|         | P |   |   |            |      |          |   |               |
|         | o |   |   |            |      |          |   |               |
|         | i |   |   |            |      |          |   |               |
|         | n |   |   |            |      |          |   |               |
|         | t |   |   |            |      |          |   |               |
|         | i |   |   |            |      |          |   |               |
|         | n |   |   |            |      |          |   |               |
|         | g |   |   |            |      |          |   |               |
|         | P |   |   |            |      |          |   |               |
|         | h |   |   |            |      |          |   |               |
|         | o |   |   |            |      |          |   |               |
|         | t |   |   |            |      |          |   |               |
|         | o |   |   |            |      |          |   |               |
|         | m |   |   |            |      |          |   |               |
|         | e |   |   |            |      |          |   |               |
|         | t |   |   |            |      |          |   |               |
|         | e |   |   |            |      |          |   |               |
|         | r |   |   |            |      |          |   |               |
+---------+---+---+---+------------+------+----------+---+---------------+
| **      |   |   |   |            |      |          |   |               |
| [Certif |   |   |   |            |      |          |   |               |
| ication |   |   |   |            |      |          |   |               |
| of      |   |   |   |            |      |          |   |               |
| Com     |   |   |   |            |      |          |   |               |
| pliance |   |   |   |            |      |          |   |               |
| with    |   |   |   |            |      |          |   |               |
| App     |   |   |   |            |      |          |   |               |
| licable |   |   |   |            |      |          |   |               |
| Ex      |   |   |   |            |      |          |   |               |
| ecutive |   |   |   |            |      |          |   |               |
| Orders  |   |   |   |            |      |          |   |               |
| and US  |   |   |   |            |      |          |   |               |
| Code]   |   |   |   |            |      |          |   |               |
| {.under |   |   |   |            |      |          |   |               |
| line}** |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
| By      |   |   |   |            |      |          |   |               |
| sub     |   |   |   |            |      |          |   |               |
| mitting |   |   |   |            |      |          |   |               |
| the     |   |   |   |            |      |          |   |               |
| p       |   |   |   |            |      |          |   |               |
| roposal |   |   |   |            |      |          |   |               |
| ide     |   |   |   |            |      |          |   |               |
| ntified |   |   |   |            |      |          |   |               |
| in this |   |   |   |            |      |          |   |               |
| *Cover  |   |   |   |            |      |          |   |               |
| Sheet/P |   |   |   |            |      |          |   |               |
| roposal |   |   |   |            |      |          |   |               |
| S       |   |   |   |            |      |          |   |               |
| ummary* |   |   |   |            |      |          |   |               |
| in      |   |   |   |            |      |          |   |               |
| r       |   |   |   |            |      |          |   |               |
| esponse |   |   |   |            |      |          |   |               |
| to this |   |   |   |            |      |          |   |               |
| R       |   |   |   |            |      |          |   |               |
| esearch |   |   |   |            |      |          |   |               |
| Announ  |   |   |   |            |      |          |   |               |
| cement, |   |   |   |            |      |          |   |               |
| the     |   |   |   |            |      |          |   |               |
| Auth    |   |   |   |            |      |          |   |               |
| orizing |   |   |   |            |      |          |   |               |
| O       |   |   |   |            |      |          |   |               |
| fficial |   |   |   |            |      |          |   |               |
| of the  |   |   |   |            |      |          |   |               |
| pr      |   |   |   |            |      |          |   |               |
| oposing |   |   |   |            |      |          |   |               |
| inst    |   |   |   |            |      |          |   |               |
| itution |   |   |   |            |      |          |   |               |
| (or the |   |   |   |            |      |          |   |               |
| ind     |   |   |   |            |      |          |   |               |
| ividual |   |   |   |            |      |          |   |               |
| p       |   |   |   |            |      |          |   |               |
| roposer |   |   |   |            |      |          |   |               |
| if      |   |   |   |            |      |          |   |               |
| there   |   |   |   |            |      |          |   |               |
| is no   |   |   |   |            |      |          |   |               |
| pr      |   |   |   |            |      |          |   |               |
| oposing |   |   |   |            |      |          |   |               |
| insti   |   |   |   |            |      |          |   |               |
| tution) |   |   |   |            |      |          |   |               |
| as      |   |   |   |            |      |          |   |               |
| ide     |   |   |   |            |      |          |   |               |
| ntified |   |   |   |            |      |          |   |               |
| below:  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
| -   ce  |   |   |   |            |      |          |   |               |
| rtifies |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    that |   |   |   |            |      |          |   |               |
|     the |   |   |   |            |      |          |   |               |
|     sta |   |   |   |            |      |          |   |               |
| tements |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    made |   |   |   |            |      |          |   |               |
|     in  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    this |   |   |   |            |      |          |   |               |
|     p   |   |   |   |            |      |          |   |               |
| roposal |   |   |   |            |      |          |   |               |
|     are |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    true |   |   |   |            |      |          |   |               |
|     and |   |   |   |            |      |          |   |               |
|     c   |   |   |   |            |      |          |   |               |
| omplete |   |   |   |            |      |          |   |               |
|     to  |   |   |   |            |      |          |   |               |
|     the |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    best |   |   |   |            |      |          |   |               |
|     of  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
| his/her |   |   |   |            |      |          |   |               |
|     kno |   |   |   |            |      |          |   |               |
| wledge; |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
| -       |   |   |   |            |      |          |   |               |
|  agrees |   |   |   |            |      |          |   |               |
|     to  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|  accept |   |   |   |            |      |          |   |               |
|     the |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    obli |   |   |   |            |      |          |   |               |
| gations |   |   |   |            |      |          |   |               |
|     to  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|  comply |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    with |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    NASA |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|   award |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|   terms |   |   |   |            |      |          |   |               |
|     and |   |   |   |            |      |          |   |               |
|     con |   |   |   |            |      |          |   |               |
| ditions |   |   |   |            |      |          |   |               |
|     if  |   |   |   |            |      |          |   |               |
|     an  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|   award |   |   |   |            |      |          |   |               |
|     is  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    made |   |   |   |            |      |          |   |               |
|     as  |   |   |   |            |      |          |   |               |
|     a   |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|  result |   |   |   |            |      |          |   |               |
|     of  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    this |   |   |   |            |      |          |   |               |
|     pr  |   |   |   |            |      |          |   |               |
| oposal; |   |   |   |            |      |          |   |               |
|     and |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
| -   c   |   |   |   |            |      |          |   |               |
| onfirms |   |   |   |            |      |          |   |               |
|     com |   |   |   |            |      |          |   |               |
| pliance |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    with |   |   |   |            |      |          |   |               |
|     all |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    prov |   |   |   |            |      |          |   |               |
| isions, |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|  rules, |   |   |   |            |      |          |   |               |
|     and |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|   stipu |   |   |   |            |      |          |   |               |
| lations |   |   |   |            |      |          |   |               |
|     set |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|   forth |   |   |   |            |      |          |   |               |
|     in  |   |   |   |            |      |          |   |               |
|     the |   |   |   |            |      |          |   |               |
|     two |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
| Certifi |   |   |   |            |      |          |   |               |
| cations |   |   |   |            |      |          |   |               |
|     co  |   |   |   |            |      |          |   |               |
| ntained |   |   |   |            |      |          |   |               |
|     in  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    this |   |   |   |            |      |          |   |               |
|     NRA |   |   |   |            |      |          |   |               |
|     \[  |   |   |   |            |      |          |   |               |
| namely, |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    (i*) |   |   |   |            |      |          |   |               |
|     As  |   |   |   |            |      |          |   |               |
| surance |   |   |   |            |      |          |   |               |
|     of  |   |   |   |            |      |          |   |               |
|     Com |   |   |   |            |      |          |   |               |
| pliance |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    with |   |   |   |            |      |          |   |               |
|     the |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    NASA |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|    Regu |   |   |   |            |      |          |   |               |
| lations |   |   |   |            |      |          |   |               |
|     P   |   |   |   |            |      |          |   |               |
| ursuant |   |   |   |            |      |          |   |               |
|     to  |   |   |   |            |      |          |   |               |
|     Non |   |   |   |            |      |          |   |               |
| discrim |   |   |   |            |      |          |   |               |
| ination |   |   |   |            |      |          |   |               |
|     in  |   |   |   |            |      |          |   |               |
|     Fe  |   |   |   |            |      |          |   |               |
| derally |   |   |   |            |      |          |   |               |
|     A   |   |   |   |            |      |          |   |               |
| ssisted |   |   |   |            |      |          |   |               |
|     Pro |   |   |   |            |      |          |   |               |
| grams*, |   |   |   |            |      |          |   |               |
|     *a  |   |   |   |            |      |          |   |               |
| nd (ii) |   |   |   |            |      |          |   |               |
|     C   |   |   |   |            |      |          |   |               |
| ertific |   |   |   |            |      |          |   |               |
| ations, |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
|   Discl |   |   |   |            |      |          |   |               |
| osures, |   |   |   |            |      |          |   |               |
|     And |   |   |   |            |      |          |   |               |
|     Ass |   |   |   |            |      |          |   |               |
| urances |   |   |   |            |      |          |   |               |
|     Re  |   |   |   |            |      |          |   |               |
| garding |   |   |   |            |      |          |   |               |
|     L   |   |   |   |            |      |          |   |               |
| obbying |   |   |   |            |      |          |   |               |
|     and |   |   |   |            |      |          |   |               |
|     De  |   |   |   |            |      |          |   |               |
| barment |   |   |   |            |      |          |   |               |
|     &   |   |   |   |            |      |          |   |               |
|     Su  |   |   |   |            |      |          |   |               |
| spensio |   |   |   |            |      |          |   |               |
| n*\]*.* |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
| Willful |   |   |   |            |      |          |   |               |
| pr      |   |   |   |            |      |          |   |               |
| ovision |   |   |   |            |      |          |   |               |
| of      |   |   |   |            |      |          |   |               |
| false   |   |   |   |            |      |          |   |               |
| info    |   |   |   |            |      |          |   |               |
| rmation |   |   |   |            |      |          |   |               |
| in this |   |   |   |            |      |          |   |               |
| p       |   |   |   |            |      |          |   |               |
| roposal |   |   |   |            |      |          |   |               |
| and/or  |   |   |   |            |      |          |   |               |
| its     |   |   |   |            |      |          |   |               |
| sup     |   |   |   |            |      |          |   |               |
| porting |   |   |   |            |      |          |   |               |
| doc     |   |   |   |            |      |          |   |               |
| uments, |   |   |   |            |      |          |   |               |
| or in   |   |   |   |            |      |          |   |               |
| reports |   |   |   |            |      |          |   |               |
| r       |   |   |   |            |      |          |   |               |
| equired |   |   |   |            |      |          |   |               |
| under   |   |   |   |            |      |          |   |               |
| an      |   |   |   |            |      |          |   |               |
| ensuing |   |   |   |            |      |          |   |               |
| award,  |   |   |   |            |      |          |   |               |
| is a    |   |   |   |            |      |          |   |               |
| c       |   |   |   |            |      |          |   |               |
| riminal |   |   |   |            |      |          |   |               |
| offense |   |   |   |            |      |          |   |               |
| (U.S.   |   |   |   |            |      |          |   |               |
| Code,   |   |   |   |            |      |          |   |               |
| Title   |   |   |   |            |      |          |   |               |
| 18,     |   |   |   |            |      |          |   |               |
| Section |   |   |   |            |      |          |   |               |
| 1001).  |   |   |   |            |      |          |   |               |
|         |   |   |   |            |      |          |   |               |
| **[NASA |   |   |   |            |      |          |   |               |
| PR      |   |   |   |            |      |          |   |               |
| OCEDURE |   |   |   |            |      |          |   |               |
| FOR     |   |   |   |            |      |          |   |               |
| H       |   |   |   |            |      |          |   |               |
| ANDLING |   |   |   |            |      |          |   |               |
| PRO     |   |   |   |            |      |          |   |               |
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+---------+---+---+---+------------+------+----------+---+---------------+
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| Nu      |   | 5 |   |            | *Fax |          | 5 |               |
| mber:** |   | 0 |   |            | N    |          | 0 |               |
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+---------+---+---+---+------------+------+----------+---+---------------+
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|         |   | a |   |            |      |          |   |               |
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|         |   | a |   |            |      |          |   |               |
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|         |   | a |   |            |      |          |   |               |
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|         |   | > |   |            |      |          |   |               |
+---------+---+---+---+------------+------+----------+---+---------------+
| **Co-Pr |   |   |   |            | **Au |          |   |               |
| incipal |   |   |   |            | thor |          |   |               |
| Inves   |   |   |   |            | ized |          |   |               |
| tigator |   |   |   |            | I    |          |   |               |
| Signat  |   |   |   |            | nsti |          |   |               |
| ures:** |   |   |   |            | tuti |          |   |               |
|         |   |   |   |            | onal |          |   |               |
|         |   |   |   |            | Offi |          |   |               |
|         |   |   |   |            | cial |          |   |               |
|         |   |   |   |            | Sign |          |   |               |
|         |   |   |   |            | atur |          |   |               |
|         |   |   |   |            | e:** |          |   |               |
+---------+---+---+---+------------+------+----------+---+---------------+
| **      |   |   |   |            | *    |          |   |               |
| Date:** |   |   |   |            | *Dat |          |   |               |
|         |   |   |   |            | e:** |          |   |               |
+---------+---+---+---+------------+------+----------+---+---------------+

  ----------------------- -- --------------- ---------- ------------------------------------------ ----------------- ------------- ------------ -- --
  **Co-Investigators:**                                                                                                                            

  **Name**                   **Telephone**              **Email**                                  **Institution**   **Address**                   

  Philip Russell             650 604-5404               [prussell@mail.arc.nasa.gov]{.underline}   NASA Ames                       Moffett         
                                                                                                   Research Center                 Field, CA       
                                                                                                                                   94035           

  James Eilers               650 604-6536               [jeilers@mail.arc.nasa.gov]{.underline}    NASA Ames                       Moffett         
                                                                                                   Research Center                 Field, CA       
                                                                                                                                   94035           

  Brent Holben               301 614-6658               <brent@aeronet.gsfc.nasa.gov>              NASA GSFC                       Greenbelt,      
                                                                                                                                   MD 20771        

  Oleg Dubovik               301 614-6624               <dubovik@aeronet.gsfc.nasa.gov>            GEST Center/UMBC                Greenbelt,      
                                                                                                   and NASA GSFC                   MD 20771        

  **Budget:**                                                                                                                                      

  Year 1 (June 2003-May                      \$294.7k                                                                                              
  2004):                                                                                                                                           

  Year 2 (June 2004-May                      \$304.5k                                                                                              
  2005):                                                                                                                                           

  Year 3 (June 2005-May                      \$308.9k                                                                                              
  2006):                                                                                                                                           

  **Total:**                                 \$908.1k                                                                                              
  ----------------------- -- --------------- ---------- ------------------------------------------ ----------------- ------------- ------------ -- --

**TABLE OF CONTENTS**

[1 ACRONYMS 1](#acronyms)

[2 ABSTRACT 2](#abstract)

[3 BACKGROUND AND RATIONALE 3](#background-and-rationale)

[4 EXAMPLES OF PREVIOUS RESEARCH RELEVANT TO THIS PROPOSAL
5](#examples-of-previous-research-relevant-to-this-proposal)

[4.1 AATS - AERONET comparisons 5](#aats---aeronet-comparisons)

[4.2 Satellite Validation with AATS-14 and AERONET
7](#satellite-validation-with-aats-14-and-aeronet)

[4.2.1 MODIS Retrievals in SAFARI 2000.
7](#modis-retrievals-in-safari-2000.)

[4.2.2 MISR Retrievals in SAFARI 2000.
8](#misr-retrievals-in-safari-2000.)

[4.2.3 SeaWiFS Retrievals in ACE-Asia.
9](#seawifs-retrievals-in-ace-asia.)

[4.3 Aerosol and H~2~O vertical profiles
10](#aerosol-and-h2o-vertical-profiles)

[4.3.1 AATS-14 Profiles for Closure Among Suborbital Measurements
10](#aats-14-profiles-for-closure-among-suborbital-measurements)

[4.3.2 AATS-14 Profiles for Tests of Chemical-Transport Models
11](#aats-14-profiles-for-tests-of-chemical-transport-models)

[5 PROPOSED RESEARCH 12](#proposed-research)

[5.1 Instrument Design 12](#instrument-design)

[5.2 Scanning Geometry and Wavelength Selection
13](#scanning-geometry-and-wavelength-selection)

[5.3 Calibration 14](#calibration)

[5.4 Data Inversion 14](#data-inversion)

[5.4.1 Retrieval of particle volume size distribution
15](#retrieval-of-particle-volume-size-distribution)

[5.4.2 Retrieval of aerosol single scattering albedo ω~0~( λ), or
complex refractive index k( λ) and  n( λ)
15](#retrieval-of-aerosol-single-scattering-albedo-ω0-λ-or-complex-refractive-index-k-λ-and-n-λ)

[5.4.3 Influence of inhomogeneity and non-sphericity on accuracy of
individual retrievals
16](#influence-of-inhomogeneity-and-non-sphericity-on-accuracy-of-individual-retrievals)

[5.4.4 Adaptation of inversion procedure for proposed ASAP instrument
16](#adaptation-of-inversion-procedure-for-proposed-asap-instrument)

[5.5 Initial validation of ASAP results
16](#initial-validation-of-asap-results)

[5.6 Potential scientific contributions in future field experiments
16](#potential-scientific-contributions-in-future-field-experiments)

[6 REFERENCES 17](#references)

[7 MANAGEMENT PLAN 20](#management-plan)

[7.1 Roles of PI's and Co-I's 20](#roles-of-pis-and-co-is)

[8 BUDGET 22](#budget)

[8.1 General Budget 22](#general-budget)

[8.2 Travel budget 23](#travel-budget)

[9 VITAE 24](#vitae)

[10 CURRENT AND PENDING SUPPORT , PI's (B. Schmid and J. Redemann)
33](#current-and-pending-support-pis-b.-schmid-and-j.-redemann)

[11 APPENDIX A: Ames Airborne Tracking Sunphotometer, AATS-14
34](#appendix-a-ames-airborne-tracking-sunphotometer-aats-14)

[12 APPENDIX B: Ames Airborne Sensor Facility Calibration Laboratory
Capabilities
36](#appendix-b-ames-airborne-sensor-facility-calibration-laboratory-capabilities)

# ACRONYMS

  ------------------- ------------------ --------------------------------------------------
  AATS-6 (14)                            6 (14)-channel Ames Airborne Tracking
                                         Sunphotometer

  ACE                                    Aerosol Characterization Experiment

  ADAM                                   Asian Dust Above Monterey

  AERONET                                Aerosol Robotic Network

  AOD                                    Aerosol Optical Depth

  ARM                                    Atmospheric Radiation Measurement

  ASAP                                   Airborne Sun-sky Auto-pointing Photometer

  ATSR                                   Along Track Scanning Radiometer

  AVHRR                                  Advanced Very High Resolution Radiometer

  CIRPAS                                 Center for Interdisciplinary Remotely Piloted
                                         Aircraft Studies

  CRD                                    Cavity Ring-Down

  CTM                                    Chemical Transport Model

  CW                                     Continuous Wave

  CWV                                    Column Water Vapor

  DOE                                    Department of Energy

  EOS                                    Earth Observing System

  GMS                                    Geostationary Meteorological Satellite

  GOCART                                 Global Ozone Chemistry Aerosol Radiation Transport

  GOES                                   Geostationary Operational Environmental Satellite

  INDOEX                                 Indian Ocean Experiment

  INTEX-NA            Intercontinental   
                      Chemical Transport 
                      Experiment-North   
                      America            

  IOP                 Intensive          
                      Observation Period 

  MATCH                                  Model of Atmospheric Transport and CHemistry

  MISR                                   Multi-angle Imaging Spectro-Radiometer

  MODIS                                  Moderate-resolution Imaging Spectroradiometer

  NIR                                    Near Infra-Red

  ONR                                    Office of Naval Research

  PBL                                    Planetary boundary layer

  PRIDE                                  Puerto RIco Dust Experiment

  SAFARI                                 Southern African Regional Science Initiative

  SeaWiFS                                Sea-viewing Wide-Field-of-view Sensor

  SGP                                    Southern Great Plains

  SSA                                    Single Scattering Albedo

  TARFOX                                 Tropospheric Aerosol Radiative Forcing
                                         Observational Experiment

  TOMS                                   Total Ozone Mapping Spectrometer

  UCAR                                   University Corporation for Atmospheric Research
  ------------------- ------------------ --------------------------------------------------

# ABSTRACT

We propose the development of a prototype airborne pointing radiometer
to measure spectrally resolved direct solar beam transmission and sky
radiances and propose its initial deployment to test its measurement
capabilities. At a minimum, the new instrument would contribute to
answering two of the five fundamental questions posed by NASA's Earth
Science Enterprise program; namely "What are the primary forcings of the
Earth system (Forcing)?" and "How well can we predict future changes in
the Earth (Prediction)?". Such contributions would be in the form of
airborne measurements of the spatial variation (both horizontal and
vertical) of aerosol optical depth, single scattering albedo, and size
distribution. Such measurements could be used to:

1)  support AURA validation plans by providing comparative measurements
    for the aerosol data to be collected by the OMI instrument,

2)  provide input to and/or test aerosol transport/climate models,

3)  support CALIPSO validation plans by providing comparative
    measurements of aerosol vertical profiles,

4)  identify the absorption signature of black carbon aerosol on local
    scales to support the development of satellite sensor retrieval
    algorithms (localized aerosol model adjustments),

5)  assess the vertical distribution of absorbing aerosol to investigate
    the implications for black carbon lifetime and long-range transport,

6)  fill in spatial gaps in aerosol observations between existing
    AERONET station measurements.

By combining the airborne capabilities of the current NASA Ames Airborne
Tracking Sunphotometers (AATS) with the expertise on measurement and
inversion of sky-radiances within the AERONET group we feel uniquely
qualified to develop a new instrument prototype to perform airborne
sky-radiance measurements. The observations of such a new instrument
would bridge the gap between the current AERONET and AATS observations,
thereby giving new insights into the spatial distributions of absorbing
aerosols and hence aerosol-climate interactions.

# BACKGROUND AND RATIONALE 

A major uncertainty in predicting possible future changes to the Earth
system in general, and its climate in particular, stems from the
necessary inclusion of atmospheric aerosols in climate models. The
current low confidence in the estimates of aerosol--induced
perturbations of Earth's radiation balance is caused by the highly
non-uniform compositional, spatial and temporal distribution of
tropospheric aerosols owing to their heterogeneous sources and short
lifetimes. Because of their short lifetimes, aerosols are most
conveniently studied using space-borne sensors \[*Kaufman et al.*, 2002;
*Ramanathan et al*., 2002\] (e.g., using MODIS on Terra and Aqua, MISR
on Terra, OMI on Aura, and CALIPSO). However, to maximize the usefulness
of space-based measurements it is mandatory to validate them frequently
and continuously.

The AErosol RObotic NETwork (AERONET) (*Holben et al*., 1998) of \~200
identical globally distributed sun and sky scanning ground-based
automated radiometers provides measurements of aerosol optical
properties, based on ten years of observations in some locations. These
data have the potential to narrow the uncertainty in knowledge of the
aerosol optical properties and are therefore used extensively in
satellite sensor validation studies. The spectral sky-radiance is
measured in a wide angular range from the sun and is minimally affected
by surface reflectance (c.f. *Dubovik et al*., 2000). AERONET imposes
instrument, calibration and processing standards that allow quantitative
results to be intercomparable between all globally distributed sites
throughout the decade long record of observatons (*Holben et al.,* 1998,
*Holben et al*., 2001, *Smirnov et al.*, 2000). The new AERONET
inversion algorithm (*Dubovik and King*, 2000) provides improved aerosol
retrievals by fitting the entire measured field of radiances - sun
radiance and the angular distribution of sky radiances - at four
wavelengths (0.44, 0.67, 0.87 and 1.02 μm) to a radiative transfer
model. The radiation field is driven by the (wavelength dependent)
aerosol complex index of refraction and the particle size distribution
(in the size range: 0.05 \< r  \< 15 μm) in the total atmospheric
column. Using such a general aerosol model in the retrieval algorithm
allows us to derive the aerosol properties with minimal assumptions.
Only spectral and size smoothness constraints are used, preventing
unrealistic oscillations in either parameter (*Dubovik and King*, 2000).
The ground-based measurements of aerosol optical depth carried out by
AERONET have been invaluable in providing continuous statistically
relevant aerosol observations in support of satellite sensor validations
and aerosol characterization. In addition, the inversion of AERONET
sky-radiance measurements to retrieve aerosol size and refractive index
information has aided in the regional adjustments of MODIS aerosol
retrieval algorithms (by providing regionally representative aerosol
single scattering albedos) and in the general assessment of
aerosol-climate interactions.

The existing NASA Ames Airborne Tracking Sunphotometers (AATS-6 and
AATS-14) measure direct solar beam transmission at 6 and 14 wavelengths
(380-1021 and 354-2139 nm, respectively), yielding aerosol optical depth
(AOD) spectra and column water vapor (CWV). Vertical differentiation of
these data in suitable flight patterns yields extinction spectra and
water vapor concentration. The deployments of AATS-6 and AATS-14 in the
Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX,
1996), the second Aerosol Characterization Experiment (ACE-2, 1997), the
Puerto Rico Dust Experiment (PRIDE, 2000), the Southern African Regional
Science Initiative (SAFARI-2000), the Asian-Pacific Aerosol
Characterization Experiment (ACE-Asia, 2001), and the Chesapeake
Lighthouse & Aircraft Measurements for Satellites (CLAMS, 2001) have
made significant contributions to the airborne study of atmospheric
aerosols (e.g., *Russell et al*., 1999, *Schmid et al*., 2000,
*Livingston et al*., 2002, *Schmid et al.*, 2002, *Redemann et al*.,
2002a, b). The AATS instruments' measurements of aerosol optical depth
are used frequently in closure studies to investigate how representative
the in situ measurements of aerosol optical properties on various
airborne platforms are \[*Hegg et al*., 1997, *Hartley et al*., 2000,
*Schmid et al*., 2000, *Magi et al*., 2002\]. They have also been used
extensively in the validation of satellite sensors aboard the NASA EOS
Terra platform, providing important aerosol information used in the
revision of retrieval algorithms for the MISR and MODIS sensors
\[*Schmid et al*., 2002, *Livingston et al*., 2002, *Levy et al*.,
2002\].

Most recently, the airborne AATS observations have been used to evaluate
the performance of aerosol transport models (*Chin and Ginoux*., 2002,
*Colarco et al*., 2002). *Kinne et al*. \[2002\] have presented
comparisons of AERONET observations to a number of climate/transport
models. The validation of such transport models is considered to be a
crucial step in assessing these models' capabilities in predicting
future climate change by treating and representing aerosol/climate
interactions properly.

Notable shortcomings of the AATS direct solar beam transmission
measurements are the lack of information on aerosol absorption and the
infrequent deployment of the instruments. The AERONET observations on
the other hand may not provide enough information on aerosols over the
oceans and do not assess the vertical distribution of aerosol
properties. Therefore, we propose here the development of a prototype
Airborne Sun/sky Auto-pointing Photometer (ASAP) which would combine the
advantages of increased aerosol information from the AERONET-like
sky-radiance measurements with the airborne tracking/pointing
capabilities of the AATS instruments. An instrument which emphasizes the
strengths of both techniques would be able to bridge an important gap
between the two types of measurements. In particular, we anticipate that
the measurements of such an instrument could make the following
scientific contributions:

1)  assess the vertical distribution of absorbing aerosol to:

    a.  support AURA validation plans by providing comparative
        measurements for the aerosol data to be collected by the OMI
        instrument,

    b.  provide input to and/or test aerosol transport/climate models,

    c.  investigate the implications for black carbon lifetime and
        long-range transport,

    d.  support CALIPSO validation plans by providing comparative
        measurements of aerosol vertical profiles,

2)  identify the absorption signature of black carbon aerosol on local
    scales to support the development of satellite sensor retrieval
    algorithms (localized aerosol model adjustments),

3)  fill in spatial gaps in aerosol observations between existing
    AERONET station measurements.

Because there are a large number of instrumental challenges, we propose
the development of a prototype. Commensurate with the outcome of the
design and feasibility studies during the first year of this study, we
anticipate the assembly of the ASAP instrument prototype in the second
and third year and a first airborne test deployment towards the end of
the third year of this grant.

# EXAMPLES OF PREVIOUS RESEARCH RELEVANT TO THIS PROPOSAL

## AATS - AERONET comparisons

Measurements by the existing NASA Ames Airborne Tracking Sunphotometer
AATS-6 have been compared to measurements from ground-based Cimel
sunphotometers during two DOE ARM IOP's, when AATS-6 was operated on the
ground to enable side-by-side comparisons of the instruments without
concern about spatial homogeneity of the observed quantity. Figure 1
shows an example of a comparison of AATS-6 and Cimel derived CWV
(columnar water vapor) and AOD (aerosol optical depth) at 380 and 1020
nm, respectively \[cf. Figure 1, panels b) and c)\]. These observations
were taken during the 1997 ARM IOP at the SGP site in Oklahoma. When
using the same line-by-line model along with the same spectroscopic
database in deriving CWV from the direct solar beam transmittance
measured by AATS-6 and the Cimel instrument, *Schmid et al*. \[2001\]
were able to show remarkable agreement in the two instruments'
observations. *Schmid et al*. \[1999\] further showed that the
concurrent measurements of aerosol optical depth in the spectral range
of 380 to 1020nm determined from the two instruments agreed to within
0.012 (rms) or better.

![](media/image2.wmf){width="6.499305555555556in"
height="2.073611111111111in"}

**Figure 1.** Statistical comparison of CWV and AOD at 380 and 1020nm as
observed by AATS-6 and a Cimel instrument during the 1997 Fall ARM IOP,
*Schmid et al*. \[1999, 2001\].

The agreement shown in Figure 1 was achieved with AATS-6 operating on
the ground only. However, there have been a number of opportunities to
compare with the data of one of the AERONET (Cimel) instruments during
fly-bys of AATS-6 or AATS-14.

For instance, Figure 2 shows a comparison of AATS-14 derived aerosol
optical depth from the CLAMS experiment in July 2001, when the
instrument operated aboard the University of Washington CV-580 aircraft.
While the agreement is again very good, the rms-differences are somewhat
larger than those in Figure 1. We attribute this to the fact that AOD
values observed in CLAMS were generally larger but also to the spatial
separation of the aircraft (AATS-14) from the ground-based AERONET
instrument. This assumption is supported by the variability estimates
shown in Figure 2.

In analogy to Figure 2, Figure 3 shows comparisons of AOD spectra
measured by various AERONET instruments and AATS-14 in SAFARI-2000
\[*Schmid et al*., 2002\]. Again, AATS-14 was operated aboard the UW
CV-580 aircraft.

![](media/image3.wmf){width="4.759722222222222in"
height="3.5659722222222223in"}

**Figure 2.** Statistical comparison of AOD at 380, 500, \~870 and
\~1020nm as observed by AATS-14 and the COVE AERONET instrument during
fly-by's of the University of Washington CV-580 aircraft in CLAMS,
*Redemann et al*. \[2002a\]. Variability estimates represent the range
of AODs observed within a distance of 10km (light blue) and 50km (dark
blue) from the ground-based instrument.

![](media/image4.wmf){width="4.623611111111111in"
height="3.698611111111111in"}

**Figure 3.** Comparisons of AOD spectra measured by AATS-14 (during
low-level flight segments) and ground-based AERONET instruments in
SAFARI-2000, *Schmid et al*. \[2002\]. In frames k) and l) the longest
two AATS-14 wavelengths are influenced by dirt on the instruments
optical window.

## Satellite Validation with AATS-14 and AERONET 

During various field experiments, including TARFOX, ACE-2, PRIDE,
SAFARI-2000, ACE-Asia, and CLAMS, considerable effort was devoted to
coordinating aircraft measurements with satellite overpasses. Among the
satellite sensors validated are AVHRR, GMS-5, GOES-8 imager, MISR,
MODIS, SeaWiFS, TOMS and ATSR-2. The aircraft measurements include
aerosol optical depth spectra measured by an existing Ames Airborne
Tracking Sunphotometer (AATS-14 or AATS-6). When measured on transects
flown near the land or ocean surface, such optical depth spectra are
useful for validating products from the satellite sensors. This section
presents a number of such validation efforts with AATS-14 and/or
AERONET.

### MODIS Retrievals in SAFARI 2000.

In SAFARI-2000, AATS-14 measured aerosol optical depth spectra aboard
the UW CV-580 in the vicinity of Inhaca Island, Mozambique on August 24,
2000. Figure 4 (left) shows the comparison of AATS-14-derived to
MODIS-derived aerosol optical thickness \[*Schmid et al*., 2002\] as a
function of wavelength.

![](media/image5.wmf){width="6.486111111111111in"
height="2.557638888888889in"}

**Figure 4.** Comparisons of AOD spectra measured by AATS-14 and
MODIS-Terra in SAFARI-2000, *Schmid et al*. \[2002\].

Also shown in Figure 4 are the concurrent AERONET measurements of AOD.
The AATS-14 measurements shown represent the first published validation
efforts of MODIS-derived AODs beyond 1.02µm, although efforts to add
similar capabilities to existing ground-based radiometers are underway
at NASA GSFC. Based on these and similar comparisons involving biomass
burning aerosol, the MODIS team adjusted the single scattering albedo in
the MODIS inversion algorithm to account for regional and seasonal
variations. The new inversion algorithm (labeled "MODIS ver4" in Figure
4, right panel) yields considerably better agreement with AERONET and
AATS-14 observations \[*Chu et al*., 2002\].

While the agreement between AATS-14 and MODIS AOD (version 4) for this
case study is rather good, Figure 4 (left panel) also illustrates the
lack of validation of the longest MODIS wavelength channel at 2.13µm.
Recently, *Dufresne et al.* \[2001\] emphasized the importance of
considering scattering of mineral aerosol in the near-IR and IR region
for accurate estimates of their radiative forcing. In addition, MODIS
bands 5-7 (1.24, 1.64 and 2.13µm) and 26 (1.37µm) are used heavily in
retrievals of cloud and land surface properties. Hence, an accurate
estimation of aerosol optical depth in this wavelength region would both
improve our understanding of aerosol climate forcing and increase our
confidence in atmospheric corrections to the MODIS channels used for
land and cloud property retrievals. AATS-14 has recently been modified
to include a channel at 2.139μm. The instrument will be employed in ADAM
(Asian Dust Above Monterey), an experiment to study Asian dust
transported across the Pacific Ocean to the US West Coast in April of
2003. Furthermore, AATS-14 will participate in the Oklahoma ARM IOP in
May/June of 2003. Both of these experiments are expected to provide
important information on the usefulness of the 2.1μm channel in
assessing the large particle mode of the aerosol size distribution.

### MISR Retrievals in SAFARI 2000.

During SAFARI-2000, AATS-14 was instrumental in identifying problems in
the initial standard MISR retrievals of aerosol optical depth. Some of
these problems were instrumental, while others pertained to the
completeness of look-up tables used in the inversion of MISR radiance
measurements to aerosol optical depth \[*Schmid et al*., 2002\]. As an
illustration, the MISR AOD(λ) retrievals shown in Figure 5 come from the
"beta" version of the standard retrieval, which is an early post launch,
unvalidated version of the algorithm. This retrieval is based on a list
of prescribed aerosol mixture models. Each mixture is tested in terms of
how well it reproduces the MISR-measured path radiances \[*Martonchik et
al*., 1998; *Kahn et al.,* 2001\]. Figure 5 shows the comparison of MISR
retrieved AOD(λ) with AATS-14 during a low altitude pass of the
Convair-580 within two adjacent 17.6×17.6 km^2^ MISR regions off the
Namibian Coast on September 11, 2000. In both regions, the "Clean
Maritime" mixture (45% sulfate, 40% sea salt and 15% sea salt coarse)
leads to good agreement at 558 nm and 672 nm; however, the MISR-derived
AOD spectrum is too flat. The "Industrial Maritime" mixture (70%
sulfate, 10% sea salt, 20% black carbon) leads to a spectral slope
agreeing with AATS-14 but the MISR AOD values are then too high. The
MISR algorithm finds a different best-fit mixture in the two adjacent
regions, leading to a large change in best-fit AOD whereas AATS-14
indicates very little change in AOD.

This spectral AOD comparison and others analyzed by the MISR team
indicate that the "beta" version of the MISR algorithm does not contain
enough small particles. It should be noted that while AATS-14 was
helpful in identifying a problem with the MISR "beta" version
retrievals, there is not sufficient information in the AATS-14 derived
AOD spectrum to determine which one of the MISR particle models is
likely responsible for the AATS-14 observed AOD spectrum. In other
words, AATS-14 is able to provide an AOD spectrum but cannot supply
information to validate a specific aerosol model used in the inversion
of satellite sensor radiances. An instrument that would provide
information on aerosol size and refractive index such as the ASAP
instrument proposed here would hence be vastly superior in validating
the aerosol models used in the inversion of satellite sensor data.

![](media/image6.wmf){width="7.33125in" height="2.7895833333333333in"}

**Figure 5.** Comparison of aerosol optical depth spectra in two
adjacent MISR pixels off the coast of Namibia, during SAFARI-2000,
\[*Schmid et al*., 2002\].

### SeaWiFS Retrievals in ACE-Asia. 

In the Spring 2001 phase of the Asian Pacific Regional Aerosol
Characterization Experiment (ACE-Asia), the 6-channel NASA Ames Airborne
Tracking Sunphotometer (AATS-6) operated on 15 of the 19 research
flights of the NCAR C-130, while its 14-channel counterpart (AATS-14)
flew successfully on all 19 research flights of the CIRPAS Twin Otter.
ACE-Asia studied aerosol outflow from the Asian continent to the Pacific
basin. It was designed to integrate suborbital and satellite
measurements and models so as to reduce the uncertainty in calculations
of the climate forcing due to aerosols. The comparisons of AATS-14 and
SeaWiFS analyzed to date (e.g., Figure 6) yield good agreement if the
4-wavelength *Hsu et al*. (2002) algorithm is used, but disagreement if
the standard SeaWiFS algorithm is applied.

![](media/image7.wmf){width="6.638888888888889in"
height="2.479861111111111in"}

**Figure 6.** Comparison of spectral aerosol optical depth on April 9
and 14, 2001 between AATS-14 and SeaWiFS, using the new 4-wavelengths
algorithm by *Hsu et al*. (2002).

## Aerosol and H~2~O vertical profiles 

From AATS direct solar beam transmission measurements we derive spectral
aerosol optical depths AOD(λ), columnar water vapor, CWV, and columnar
ozone. Flying at different altitudes over a fixed location allows
derivation of AOD(λ) or CWV in a given layer. Data obtained in vertical
profiles allows derivation of spectral aerosol extinction *E~a~*(λ) (see
Figure 7) and water vapor density *ρ*~w~.

![](media/image8.wmf){width="3.2395833333333335in"
height="2.4291666666666667in"}![](media/image9.wmf){width="3.2381944444444444in"
height="2.44375in"}

**Figure 7.** Example of AOD profiles and derived extinctions at 13
wavelengths from 354 to 1558 nm calculated from AATS-14 measurements
acquired during an aircraft ascent south of Korea on 17 April 2001
during ACE-Asia. The two panels to the right show the analogous
procedure of deriving water vapor density from the profile of CWV. A
comparison with a standard EdgeTech Chilled Mirror instrument is also
shown.

### AATS-14 Profiles for Closure Among Suborbital Measurements

An important class of extinction closure studies addresses the question:
\"Can in situ measurements of aerosol properties account for the solar
beam attenuation (extinction) by an aerosol layer or column?\" Such
closure studies have revealed important insights about aerosol sampling
and inadvertent modification in previous experiments such as TARFOX
(*Hegg et al*., 1997; *Hartley et al*., 2000), ACE-2 (*Collins et al*.,
2000; *Schmid et al*., 2000) and SAFARI 2000 (*Magi et al*., 2002).
Instrumental is the measurement of aerosol optical depth and columnar
water vapor with an Ames Airborne Tracking Sunphotometer (AATS-14 or
AATS-6), because inlet effects (e.g., loss or enhancement of large
particles, shrinkage by evaporation of water, organics, or nitrates) and
filter effects are avoided.

Measuring solar beam attenuation by an AATS on the same aircraft as in
situ sensors allows a close match in the aerosol layers described by the
attenuation and in situ measurements. Such a match allows the
best-defined comparison between attenuation and in situ results. An
example from ACE-Asia where the in situ extinction is computed as the
sum of scattering (from humidified nephelometry) and absorption (PSAP
instrument) is shown in Figure 8. Figure 8 also shows a concurrently
measured aerosol extinction profile derived from a ship-based lidar
system (e.g., *Welton et al*., 2001) and values calculated from Mie
theory using measured size distributions and size-resolved composition
(used to determine the complex refractive indices) (*Wang et al*.,
2002). Column closure studies as presented in Figure 8 can illustrate
instrumental deficiencies as well as the strength of the various
techniques involved.

![](media/image10.wmf){width="4.026388888888889in" height="3.06875in"}

**Figure 8.** Comparison of aerosol extinction derived from AATS-14
measurements, aerosol size distributions, the sum of aerosol scattering
(nephelometer) and absorption (PSAP), and lidar measurements on R/V Ron
Brown during ACE-Asia for the profile shown in Figure 7.

### AATS-14 Profiles for Tests of Chemical-Transport Models

Comparisons (e.g., *Kinne et al*., 2002) of chemical-transport models
(CTMs) that predict aerosol spatial distributions show that vertical and
horizontal distributions often differ markedly from model to model.
Hence, the vertical profiles of AOD and extinction measured by airborne
sunphotometers (AATS-6 and -14) can provide a key performance test for
such CTMs. A number of such model tests have been presented by *Chin et
al*. \[2001\] for GOCART and *Colarco et al*. \[2002\] for CARMA/MATCH.

Two examples of comparisons between GOCART- and AATS-14-derived aerosol
optical depth at 525nm are shown in Figure 9, representing AATS-14
observations from consecutive days in ACE-Asia. From Figure 9, it can be
seen at what altitudes the model contributions to the total optical
depth match up with the optical depth measured by AATS-14. For instance,
the model seems to represent the total AATS-measured AOD at an altitude
of 3.5 km for the observations on April 17^th^ (Fig. 9, left panel).
However, below 3.5 km the AATS-14 observations for that day indicate
increasingly more AOD towards the surface, resulting in a considerable
AOD difference of \~0.25 at the lowest point of the profile between
model and observation. Conversely, the model and AATS-14 derived AOD at
an altitude of 3.5km on April 18^th^ (Fig. 9, right panel) show a
disagreement of 0.05. The model's increase in sulfate concentration
towards the surface however drives the total AOD to increase
proportionally to the AATS-14 derived AOD. This indicates that the model
represents the low-altitude AOD for this day well, and that any
disagreement at the surface is due to disagreement above 3.5km. As was
the case for the comparisons of AATS-14 and MISR (see section 2.2.2),
AATS-14 proves to be a reliable tool to determine aerosol optical depth.
However, the lack of information on aerosol microphysical properties in
AATS-14 observations will make it difficult to assess which model
aerosol constituent may be in error. Again, an airborne Sun-sky-radiance
instrument that would provide information on aerosol microphysics such
as proposed here could provide a more detailed validation of transport
models beyond the already valuable insight into the vertical
distribution of AOD as provided by the existing AATS-14.

![](media/image11.wmf){width="4.3277777777777775in"
height="3.2472222222222222in"}

**Figure 9.** Comparison of the vertical distribution of aerosol optical
depth at 525nm between AATS-14 and GOCART for profiles during two
consecutive days in ACE-Asia.

# PROPOSED RESEARCH

## Instrument Design

The mechanical design of the ASAP instrument prototype proposed here
will be based on the tracking and pointing methods used by the existing
14-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14). Because
AATS-14 and its predecessor AATS-6 have been integrated and flown
successfully on currently operational suborbital platforms (e.g., NASA
DC-8, NCAR C-130, ONR/NPS CIRPAS Twin-Otter), such an initial design
would facilitate a cost-effective test deployment of the new instrument
prototype. To reduce design costs further, the prototype ASAP will be
based on a partly assembled second unit of AATS-14. During the first
year of the grant we propose to carry out a design study that will allow
a cost and feasibility assessment for the instrument prototype. The
initial technical challenges to overcome include the design of an optics
module that will enable the measurement of the direct solar beam
intensity and the intensity of sky-radiances as much as 5 orders of
magnitude smaller than the direct beam intensity. This is exemplified in
Fig. 10 showing a sky scan with an AERONET Cimel instrument in Zambia.
While the measurement of light intensity over such a large dynamic range
can be achieved with state-of the-art analog signal digitization, the
suppression of unwanted straylight when pointing close to the sun
presents a challenge. In the AERONET Cimel design, straylight is
suppressed using a 33 cm baffled entrance tube (straylight rejection is
10^-5^ for measurements of the aureole 3° from the sun, *Holben et al*.
1998). For the proposed instrument we will need to achieve equally
efficient stray light suppression with a about half this optical path
length to be able to integrate the optics module into the geometric
confines of the current AATS-14 instrument dome (see Appendix A, Fig.1).

## Scanning Geometry and Wavelength Selection

The AERONET Cimel CE-318 instruments operate at eight wavelengths. 340,
380, 440, 500, 670, 870, 940, and 1020 nm filters embedded in a filter
wheel are standard. Sky radiance measurements are made at 440, 670, 870
and 1020 nm. Two basic sky observation sequences are made, the
"almucantar" and "principal plane". The philosophy is to acquire aureole
and sky radiances observations through a large range of scattering
angles from the sun and when combined with the direct sun measurements
to retrieve aerosol size distribution, aerosol complex refractive index,
and aerosol optical depth. An almucantar is a series of measurements
taken at the elevation angle of the Sun for specified azimuth angles
relative to the position of the sun. In a principal plane scan the
azimuth remains fixed at the solar azimuth and measurements are taken at
specified elevation angles.

The AATS-14 measures simultaneously at 14 wavelengths between 353 and
2139 nm (see Appendix A, Fig. 2). The number and choice of wavelengths
for the proposed ASAP will depend on the design of the optics module. We
will try to retain as many AATS-14 wavelengths as possible. In
particular, we plan to retain the recently extended spectral range
covered with the AATS-14 wavelengths, which is expected to well
constrain the inversion within the larger particle size range. We plan
to adhere to the basic sky observation sequences, almucantar and
principal plane, when taking measurements aboard the aircraft (in
addition to the direct beam measurements of course). Due to the
aircraft's movement, however, the sky observations will not fall exactly
on the almucantar or principal plane. Information on aircraft attitude
(yaw, pitch, and roll) will then be used to compute the scattering angle
for each observation. It should be noted that the inversion procedure
(see below) does not require the observations to follow any specific
geometrical pattern. It merely requires the observations to be carried
out over a sufficient range and number of scattering angles, and that
the scattering angles be accurately determined.

We will also pursue the option of polarization measurements of the sky
at one or two wavelengths. This additional information can help to
further constrain the retrievals of aerosol optical properties.
Polarization measurements at 870 nm are an option with the Cimel CE-318
instrument (at the cost of two wavelengths, though).

![](media/image12.wmf){width="4.978472222222222in"
height="4.845833333333333in"}

**Figure 10.** This figure illustrates the spectral and angular
variability of the diffuse radiation measured by an AERONET
Sun/sky-radiometer at the ground. Measurements were performed for
African biomass burning observed in Zambia at different aerosol
loadings: AOD at 440 nm (τ (440)) = \~0.1, \~0.5, \~2.0.

## Calibration

Calibration refers to the determination of the calibration coefficients
needed to convert the instrument output (voltages) to a desired output,
in this case AOD and radiance (W/m^2^/sr/μm). Calibration for AOD will
be achieved using the Langley plot method (e.g. *Schmid and Wehrli*,
1995) at high altitude sites away from pollution sources. The AATS and
AERONET teams routinely use the Mauna Loa Observatory on the Big Island
of Hawaii for that purpose. We plan to use the same site for the AOD
calibration of the proposed ASAP instrument. The radiance calibration
will be achieved using integrating spheres at the Ames Airborne Sensor
Facility (see Appendix B). Furthermore we will perform intercomparisons
between ASAP and the NASA Goddard AERONET reference instruments at the
Goddard rooftop facility.

## Data Inversion

To invert the data obtained with ASAP we will use the inversion
procedure used for AERONET (*Dubovik and King*, 2000) with alterations
specifically tailored to the planned airborne instrument (see below).
The current AERONET inversion algorithm (see section 1) was developed by
Dr. Oleg Dubovik (Co-I of this proposal). The accuracy of individual
AERONET retrievals was analyzed by extensive sensitivity simulations
(*Dubovik et al.,* 2000), studying the effects of both random
measurement errors and systematic instrumental offsets for several
aerosol models.

### Retrieval of particle volume size distribution

The retrieval of the particle volume size distribution was demonstrated
to be adequate in practically all situations (e.g., AOD (440 nm) ≥
0.05), as demonstrated by *Dubovik et al*. (2000). These studies show
that the error of the retrieved volume density *d*V(*r*)/dln *r* changes
as a nonlinear function of particle size, aerosol type, and actual
values of the size distribution. In particular, for the intermediate
particle size range (0.1 ≤ r ≤ 7 μm), the retrieval errors do not exceed
10% in the maxima of the volume distribution and may increase up to
about 35% for the points corresponding to the minimum values of
*d*V(*r*)/dln*r* in this size range. For the edges (0.05 ≤ r  \< 0.1μ m
and 7 \< r ≤ 15 μ m) of the assumed particle size interval, the accuracy
of the size distribution retrieval drops significantly, because of the
low sensitivity of the aerosol scattering at 440, 670, 870 and 1020 nm
to particles of these sizes. Correspondingly, the retrieval errors rise
up to 80-100 % (and even higher) for the sizes less than 0.1 μm and
higher than 7 μm.  The high errors at the edges do not significantly
affect the derivation of the main features of the particle size
distribution (concentration, median and effective radii, etc.), because
typically the aerosol particle size distributions (*d*V(*r*)/dln*r*)
have low values at the edges of retrieval size interval.

The proposed ASAP instrument is expected to cover a significantly
broader spectral region than the AERONET/Cimel on which these
simulations were based. ASAP measurements at 1240, 1558 and 2139 nm
(even if performed on the direct solar beam only as currently done with
AATS-14) will better constrain the inversion of larger particle sizes
and thus lead to smaller retrieval errors.

### Retrieval of aerosol single scattering albedo ω~0~( λ), or complex refractive index *k*( λ) and  *n*( λ)

The analysis of *Dubovik et al.,* (2000) showed that an accurate
ω~0~( λ) retrieval (with accuracy to the level of 0.03) and complex
index of refraction (errors on the order of 30-50 % for the imaginary
part of the refractive index and 0.04 for the real part of the
refractive index) can be retrieved only for high aerosol loading (AOD
(440 nm) ≥ 0.5) and for solar zenith angle \> 50° (i.e., the range of
scattering angles in measured solar almucantar \> 100°).  For
observations with lower aerosol loading, the retrieval accuracy of
ω~0~( λ), *k*( λ) and  *n*( λ) significantly decreases because of a
decrease of the information content. Indeed, the calibration accuracy
becomes an obstacle because it causes an error in measuring AOD (δAOD
= ±0.01) that is on the order of at least of 5-10 % of the optical
thickness for AOD (440 nm) ≤ 0.2, and it is comparable with the
absorption partition in the total optical thickness.  Correspondingly,
the retrieval of ω~0~(λ ) and *k*(λ ) becomes difficult, as well as
*n*( λ), because scattering effects of *n*(λ )  and *k*(λ ) are not
completely independent. Thus, our studies (*Dubovik et al*., 2000) have
shown that for AOD (440 nm) ≤ 0.2, the accuracy levels drop down to
0.05-0.07 for ω~0~(λ ), to 80-100% for the imaginary part of the
refractive index, and to 0.05 for the real part of the refractive
index. 

The proposed airborne instrument will have the advantage of carrying out
a differential measurement (i.e. measurements at the bottom and above a
haze layer) which cancels systematic errors in the AOD or radiance
calibration and thus should lead to improved retrievals.

### Influence of inhomogeneity and non-sphericity on accuracy of individual retrievals

The aerosol particles in the retrieval are assumed to be polydispersed
homogeneous spheres. *Dubovik et al*. (2000) showed how such assumptions
bias the retrievals in the case of nonspherical aerosols or
externally/internally mixed spheres. In order to address the problems of
desert dust non-sphericity the AERONET processing of non-spherical
desert dust has recently been improved by utilizing a model of randomly
oriented spheroids (as described by *Dubovik et al.*, \[2002\]). The
results of the spheroid based retrievals show significant
improvements for desert dust aerosol.

### Adaptation of inversion procedure for proposed ASAP instrument

In modeling the radiative transfer we need to address the fact that the
measurements are taken at some distance from the ground, i.e. we will
need to account for the effect of aerosol from under the plane and the
effects of the surface.

We will need to adjust the smoothness constraints with new parameters
based on levels of accuracy in the measurements, number of spectral
channels, and spectral positions. The change in number of spectral
channels and spectral positions will also require changes in accounting
for gaseous absorption and molecular scattering.

## Initial validation of ASAP results

We expect initial validation of ASAP results from ground-based operation
collocated with AATS-14 (for AOD) and AERONET instruments (for AOD,
*d*V(*r*)/dln*r*, and ω~0~( λ)).

## Potential scientific contributions in future field experiments

Given a successful design and integration of the optics and electronics
modules into the mechanical design of AATS-14 in the second and third
year of the grant, we intend to test-fly the instrument prototype
towards the end of the third year of our study. The most cost-effective
platforms for a test deployment would be the platforms that AATS-14 has
previously flown on (see above). However, given adequate resources for
instrument integration, any of the ESE suborbital platforms identified
in Appendix F of the NRA could be considered, with preference for those
that enable extensive low-altitude flight legs.

For the continued validation of the prototype ASAP we will need to fly
low over several AERONET sites to see if the measurements compare well
to the ground-based data under several conditions, such as urban
industrial aerosol, mineral dust as well as near background conditions.
The validation can then be enhanced by flying vertical profiles over
combined AERONET and MPLNet (lidar) sites. Aerosol absorption derived
from ASAP in profiles can also be compared with absorption derived from
filter based in-situ methods (PSAP, aethalometers \[*Bond et al*.,
1999\]), in-situ photoaccoustic methods \[*Arnott et al*., 1999\],
in-situ cavity ring down methods \[*Strawa et al*., 2002\] or from flux
divergence \[*Bergstrom et al*., 2002\].

The proposed ASAP instrument will be extremely powerful for column
closure experiments and assessment of radiative forcing during field
campaigns. The strength of the ASAP is that it will allow extending the
temporally continuous point observations of AERONET and MPLNet to a
larger geographical area. ASAP will be able to measure aerosol optical
properties spectrally, vertically, and horizontally resolved. Among the
possibilities for an initial deployment are validation studies for the
space-borne lidar systems GLAS and CALIPSO, both of which will emphasize
the importance of validating vertical aerosol distributions. In
addition, we anticipate that ASAP would be an important asset in
experiments to study aerosols produced by biomass burning and other
sources in Southeast and East Asia \[e.g., the Asian Brown Cloud (ABC)
and the Biomass Aerosol and Smoke Experiment (BASE-Asia)\], as called
for in section (v) of the detailed NACIP implementation plan
\[*Ramanathan et al*., 2002\]. Under NACIP, field campaigns will be
designed to "quantify the links between aerosols and the hydrologic
cycle, to relate the aerosol forcing to aerosol types and their regional
emission sources; and to the improvement of aerosol treatment in climate
models" \[*Ramanathan et al*., 2002\], and we expect detailed
observations using the ASAP instrument to contribute to every one of
these objectives.

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dust aerosol over the ocean during PRIDE, *J. Geophys. Res.*, submitted,
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A. Allen, O. Torres, R. C. Levy, L. A. Remer, B. N. Holben, A. Smirnov,
O. Dubovik, E. J. Welton, J. Campbell, S. A. Christopher, J. Wang,
Airborne sunphotometer measurements of aerosol optical depth and
columnar water vapor during the Puerto Rico Dust Experiment, and
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Magi, B. I., P. V. Hobbs, B. Schmid, and J. Redemann, Vertical profiles
of light scattering, light absorption and single scattering albedo
during the dry, biomass burning season in southern Africa and
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optical depths*, J. Geophys. Res.*, in press, 2002.

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A., Hobbs, P. V., Kahn, R. , Smith, W. L., Holben, B. N., Rutledge, C.
K., Pitts, M. C., Mishchenko, M. I., Chowdhary, J. , Martins, J. V.,
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Measurements for Satellites) Experiment, 2001, *[EOS
Transactions]{.underline}*, Vol.83, no. 19, pp.S22-23, 2002a.

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Calculations, *Abstracts*, 11^th^ Conference on Atmospheric Radiation,
American Meteorological Society, Ogden, UT, June 3-7, pp. 35, 2002b.

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V. Hobbs, Aerosol-induced radiative flux changes off the United States
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during the Fall 1997 ARM Intensive Observation Period, *Geophys. Res.
Lett*., *17*, 2725-2728, 1999.

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Jonsson, D. R. Collins, R. C. Flagan, J. H. Seinfeld, S. Gassó, D. A.
Hegg, E. Öström, K. J. Noone, E. J. Welton, K. J. Voss, H. R. Gordon, P.
Formenti, and M. O. Andreae, Clear sky closure studies of lower
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measurements, *Tellus*, B 52, 568-593, 2000.

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J.C. Liljegren, B.N. Holben, T.F. Eck, J.M. Livingston, P.B. Russell, T.
Ingold, and I. Slutsker. Comparison of columnar water-vapor measurements
from solar transmittance methods. *Applied Optics,* Vol. 40, No. 12,
1886-1896, 2001.

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McGill, B. N. Holben, E. J. Welton, J. Campbell, O. Torres, R. A. Kahn,
D. J. Diner, M. C. Helmlinger, D. A. Chu, C. Robles Gonzalez, and G. de
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measurement of aerosol optical properties using continuous wave cavity
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Hegg, E. J. Welton, and D. Bates. Clear-column radiative closure during
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\"Global monitoring of clouds and aerosols using a network of
micro-pulse lidar systems \", in Lidar Remote Sensing for Industry and
Environmental Monitoring, U. N. Singh, T. Itabe, N. Sugimoto, (eds.),
Proc. SPIE, 4153, 151-158, 2001.

# MANAGEMENT PLAN

## Roles of PI's and Co-I's

Drs. Beat Schmid and Jens Redemann will be Co-Principal Investigators.
As such, they will be responsible for the overall scientific direction,
project management, administration, and communications with NASA HQ.
They will bw responsible for completing the work on time and within
budget.

Dr. Schmid has 10 years of experience in ground-based and airborne sun
photometry including instrument design and calibration, development and
validation of algorithms to retrieve aerosol optical depth and size
distribution, H~2~O and O~3~. He has participated in numerous
deployments of the Ames Airborne sunphotometers. He has experience in
scientific project management and administration.

Dr. Redemann has been a member of the AATS team since 1999. He has
participated in several deployments of the Ames Airborne sunphotometers.
Most recently he was the Principal Investigator for the participation of
AATS-14 in the CLAMS satellite validation study (July 2001). A junior
programmer will work under Drs. Redemann and Schmid's guidance.

Dr. Philip Russell (Co-Investigator) will assist the PI's in overall
scientific direction, project management, administration, and
communications with NASA HQ. Dr. Russell has led the development of two
NASA Ames airborne sunphotometers (AATS-6 flew first in 1985 and AATS-14
flew first in 1996).

Mr. James Eilers (Co-Investigator) will be the lead engineer for the
development of the proposed ASAP instrument. He will be supported by a
Lab Technician and by Ames Airborne Sensor Facility personnel (see
below). James Eilers was the project manager and lead engineer for the
AATS-14 Sunphotometer Rework Project. He is currently responsible for
AATS-6 and --14 maintenance and upgrades and the technical aspects of
instrument deployments (e.g., aircraft integration).

The Ames Airborne Sensor Facility (ASF) will offer support in the areas
of instrument calibration, electro-optic design consultation, and
hardware fabrication, as needed. The ASF maintains an optical
calibration laboratory specifically designed to support airborne
spectro-radiometers. It includes primary and secondary radiometric
sources, and various spectral measurement devices (see appendix B). The
laboratory is under the technical supervision of the NASA EOS
Calibration Scientist at GSFC, and is a regular participant in
"round-robin" exercises with NIST and other national facilities. This
laboratory is well suited to characterize stray-light and polarization
effects, as well as to establish fundamental system response. The ASF
also has extensive experience with the design and implementation of
optical and electronic systems for the NASA airborne science program,
including the MODIS and ASTER Airborne Simulators flown on the ER-2 and
DC-8 aircraft. Their experience with state-of-the-art analog signal
digitization and data-capture systems on these infrared systems should
prove valuable to this project. In addition, ASF engineers have many
years of collective experience in maintaining well-calibrated systems in
the problematic airborne environment. Other assets will be used as
needed, including packaging design and precision machining services.

Dr. Brent Holben (Co-Investigator) will assist the PI's in overall
scientific direction. He is the Principal Investigator of the AERONET
global network of Sun/sky photometers.

Dr. Oleg Dubovik (Co-Investigator) developed the current AERONET
inversion algorithm. He will be responsible for the adaptation of the
inversion code to retrieve physical quantities from the data expected
from the proposed ASAP. He will also support the project with simulation
studies during the design phase. A senior programmer will work under Dr.
Dubovik's guidance.

NASA Ames and Goddard will furnish additional personnel necessary to
accomplish the research.

A yearly breakdown of tasks is presented below:

+-----+----------------+-----------------------------------------------+
| Y   | June 2003 --   | -   Adapt instrument software to perform sky  |
| ear | May 2004       |     scans with AATS-14. Same software will be |
| 1   |                |     used for ASAP.                            |
|     |                |                                               |
|     |                | -   Tests of entrance optics of AATS-14       |
|     |                |     instrument. Based on the results, design  |
|     |                |     for improved straylight rejection         |
|     |                |     (baffling, lenses etc.) for ASAP.         |
|     |                |                                               |
|     |                | -   Identify and order state-of-the-art       |
|     |                |     analog signal digitization.               |
|     |                |                                               |
|     |                | -   Identify and order parts to complete      |
|     |                |     AATS-14 second unit (excl. optics module) |
|     |                |     which will be basis for ASAP.             |
+-----+----------------+-----------------------------------------------+
| Y   | June 2004 --   | -   Assembly of prototype ASAP. Tests at Ames |
| ear | May 2005       |     to compare direct beam measurements with  |
| 2   |                |     AATS-14.                                  |
|     |                |                                               |
|     |                | -   Start adaptation of inversion code.       |
+-----+----------------+-----------------------------------------------+
| Y   | June 2005 --   | -   Make modifications to prototype ASAP if   |
| ear | May 2006       |     needed. Calibration at Mauna Loa and ASF. |
| 3   |                |                                               |
|     |                | -   Measurements at Ames and Goddard near     |
|     |                |     AERONET and AATS-14 instruments.          |
|     |                |                                               |
|     |                | -   Compare results of inversion from AERONET |
|     |                |     and prototype ASAP.                       |
|     |                |                                               |
|     |                | -   Test flight prototype ASAP on CIRPAS Twin |
|     |                |     Otter (aircraft integration is trivial    |
|     |                |     because it is identical to AATS-14).      |
|     |                |                                               |
|     |                | -   Analyze results. Present preliminary      |
|     |                |     results at scientific meeting.            |
+-----+----------------+-----------------------------------------------+

# BUDGET

## General Budget

![](media/image13.wmf){width="6.995833333333334in"
height="7.461805555555555in"}

## Travel budget

![](media/image14.wmf){width="6.997222222222222in"
height="6.725694444444445in"}

# VITAE

(a) **Beat Schmid**

**Abbreviated Curriculum Vitae**

Bay Area Environmental Research Institute

NASA Ames Research Center, MS 245-5

Moffett Field, CA 94035-1000

\(650\) 604 5933

bschmid@mail.arc.nasa.gov

Education

  -------------------- --------- ------ -------------------------------------------
  M.S.                           1991   Institute of Applied Physics, University of
                                        Bern, Switzerland

  Ph.D.                          1995   Institute of Applied Physics, University of
                                        Bern, Switzerland

  Postdoctoral         1995-97          Institute of Applied Physics, University of
  Fellowship                            Bern, Switzerland
  -------------------- --------- ------ -------------------------------------------

Professional Experience

[Bay Area Environmental Research Institute]{.underline}, Sonoma, CA
(1997-Present)

Senior Research Scientist, Principal Investigator

[University of Arizona]{.underline}, Tucson, AZ (Oct. 1995 -Jan. 1996)

Visiting Scientist

[University of Bern]{.underline}, Switzerland (1989-1997)

Research Assistant (1989-1995)

Postdoctoral Researcher (1995-1997)

Scientific Contributions

-   Conducted 10 years of leading studies in ground-based and airborne
    sun photometry: instrument design and calibration, development and
    validation of algorithms to retrieve aerosol optical depth and size
    distribution, H~2~O and O~3~.

-   Participated with the NASA Ames Airborne Sun photometers in ACE-2
    (North Atlantic Regional Aerosol Characterization Experiment, 1997,
    Tenerife). Extensive comparison of results (closure studies) with
    other techniques: lidar, optical particle counters, nephelometers,
    and satellites.

-   Employed NASA Ames Airborne Sun photometers in the US Dept. of
    Energy, Atmospheric Radiation Measurement (ARM) program integrated
    fall 1997 and fall 2000 intensive observation periods in Oklahoma.
    Led sun photometer intercomparison. Extensive comparison of water
    vapor results with radiosondes, microwave radiometers, lidar, and
    Global Positioning System.

-   Operated NASA Ames Airborne Sun photometers in SAFARI 2000 (Southern
    African Regional Science Initiative; August/September 2000).
    Validation of lidar and satellite retrievals.

-   Participated with the NASA Ames Airborne Sun photometers in ACE-Asia
    (Asian Pacific Regional Aerosol Characterization Experiment; April
    2001). Closure studies, satellite and lidar validation.

-   Operated the NASA Ames Cavity Ringdown instrument in Reno Aerosol
    Optics Study (June, 2002). Comparison of aerosol extinction,
    scattering and absorption from various methods (cavitiy ring down,
    photo-acoustic, nephelometer, filter based)

-   Led planning of DOE ARM May 03 Aerosol Intensive Observation Period.
    Developed a proposed airborne payload based on the CIRPAS Twin Otter
    aircraft.

-   Evaluated candidate methods for SAGE III satellite ozone/aerosol
    separation using airborne sunphotometer data.

-   Applied NOAA/AVHRR satellite data to monitor vegetation growth in
    Switzerland

Scientific Societies/Editorships

-   Associate Editor, *Journal Geophysical Research* (2002- )

-   Member, American Geophysical Union and American Meteorological
    Society

Bibliography (selection is appended)

-   28 peer-reviewed journal articles (8 first-authored and 20
    co-authored)

-   95 (23 first-authored and 72 co-authored) conference publications

-   13 invited talks at conferences, workshops and seminars

Grants

Principal Investigator, DOE ARM Science Team.

Principal Investigator on two Cooperative Agreements between Bay Area
Environmental Research Institute and NASA Ames Research Center since
2000. Responsible for research and financial administration of 3.5
fulltime scientists.

Co-PI and Co-I on numerous research grants funded by NASA, NOAA, Office
of Naval Research (ONR) and National Science Foundation (NSF).

Selected Publications (from 28 published or in press)

Schmid B., et al., Coordinated airborne, spaceborne, and ground-based
measurements of massive, thick aerosol layers during the dry season in
Southern Africa, J. Geophys. Res., in press, 2002.

Livingston, J. M., et al., incl, B. Schmid, Airborne sunphotometer
measurements of aerosol optical depth and columnar water vapor during
the Puerto Rico Dust Experiment, and comparison with land, aircraft, and
satellite measurements, J. Geophys. Res., in press, 2002.

Wang, J., et al., incl, B. Schmid, Clear-column radiative closure during
ACE-Asia: Comparison of multiwavelength extinction derived from particle
size and composition with results from sunphotometry, J. Geophys. Res.,
in press, 2002.

Pilewskie, P., et al., incl, B. Schmid, Solar Spectral Radiative Forcing
During the South African Regional Science Initiative, J. Geophys. Res.,
in press, 2002.

Schmid B., et al., Comparison of columnar water-vapor measurements from
solar transmittance methods. Applied Optics, Vol. 40, No. 12, 1886-1896,
2001.

Schmid, B., et al., Clear sky closure studies of lower tropospheric
aerosol and water vapor during ACE 2 using airborne sunphotometer,
airborne in-situ, space-borne, and ground-based measurements, Tellus, B
52, 568-593, 2000.

Schmid B., et al., Comparison of Aerosol Optical Depth from Four Solar
Radiometers During the Fall 1997 ARM Intensive Observation Period,
Geophys. Res. Lett., 26(17), 2725-2728, 1999.

Schmid, B., P. R. Spyak, S. F. Biggar, C. Wehrli, J. Sekler, T. Ingold,
C. Mätzler, and N. Kämpfer, Evaluation of the applicability of solar and
lamp radiometric calibrations of a precision Sun photometer operating
between 300 and 1025 nm. Appl. Opt., 37(18), 3923-3941, 1998.

Schmid, B., C. Mätzler, A. Heimo, and N. Kämpfer, Retrieval of Optical
Depth and Size Distribution of Tropospheric and Stratospheric Aerosols
by Means of Sun Photometry. IEEE Geosci. Remote. Sens., 35(1), 172-182,
1997.

Schmid, B., K. J. Thome, P. Demoulin, R. Peter, C. Mätzler, and J.
Sekler, Comparison of Modeled and Empirical Approaches for Retrieving
Columnar Water Vapor from Solar Transmittance Measurements in the 0.94
Micron Region. J. Geophys. Res., 101(D5), 9345-9358, 1996.

Schmid, B., and C. Wehrli, Comparison of Sun Photometer Calibration by
Langley Technique and Standard Lamp. Appl. Opt., 34(21), 4500-4512,
1995.

(b) **Jens Redemann**

> **Abbreviated Curriculum Vitae**

Bay Area Environmental Research Institute, 560 Third Street West,
Sonoma, CA 95476

PROFESSIONAL EXPERIENCE

  --------------------- ----------------- --------------------------------
  Senior Research       BAERI, Sonoma, CA April 1999 to present
  Scientist                               

  Research Assistant    UCLA, CA          May 1995 to March 1999

  Lecturer              UCLA, CA          Jan. 1999 to present

  Research Assistant    FU Berlin,        June 1994 to April 1995
                        Germany           
  --------------------- ----------------- --------------------------------

EDUCATION

+----------------------------------+-----------------------------------+
| Ph.D. in Atmospheric Sciences,   | > 1999                            |
| UCLA.                            |                                   |
+----------------------------------+-----------------------------------+
| M.S. in Atmospheric Sciences,    | > 1997                            |
| UCLA.                            |                                   |
+----------------------------------+-----------------------------------+
| M.S. in Physics, FU Berlin,      | > 1995                            |
| Germany.                         |                                   |
+----------------------------------+-----------------------------------+

RELEVANT RESEARCH EXPERIENCE

-   NASA New Investigator Program, Principal Investigator, 2002-2005.

-   Principal Investigator for the participation of AATS-14 (a
    narrow-band radiometer) in the CLAMS satellite validation study
    (July 2001). Responsible for proposal writing and experiment design,
    instrument integration, as well as scheduling and supervision of
    three group members.

-   Developed a coupled aerosol microphysics and chemistry model to
    study the dependence of the aerosol single scattering albedo on
    ambient relative humidity.

-   Related airborne measurements using a sunphotometer, a lidar (light
    detection and ranging) system and a spectral solar flux radiometer
    to in situ measurements of atmospheric (mineral dust) aerosols and
    gases and modeled the local radiative transfer in Earth's
    atmosphere.

-   Participated in the SAFARI-2000, ACE-Asia, PRIDE and CLAMS field
    experiments aimed at investigating atmospheric aerosols. Member of
    CLAMS (Chesapeake Lighthouse Aerosol Measurements for Satellites)
    science team.

-   Utilized satellite derived aerosol optical depth fields and aerosol
    properties from the ACE-Asia campaign to determine the aerosol
    radiative forcing of climate in the Pacific Basin troposphere.

HONORS / ORGANIZATIONS

+----------------------------------------------------------+-----------+
| Invited Presentation at the 5^th^ International APEX     | #### **   |
| workshop, Miyazaki, Japan.                               | July 2002 |
|                                                          | ** {#july |
|                                                          | -2002 .un |
|                                                          | numbered} |
+----------------------------------------------------------+-----------+
| Invited Presentation at the Atmospheric Chemistry        | #### **19 |
| Colloquium for Emerging Senior Scientists (ACCESS V).    | 99** {#se |
|                                                          | ction .un |
|                                                          | numbered} |
+----------------------------------------------------------+-----------+
| Outstanding Student Paper Award, AGU Fall meeting.       | **1998**  |
+----------------------------------------------------------+-----------+
| NASA Global Change Research Fellowship Awards.           | **19      |
|                                                          | 95-1998** |
+----------------------------------------------------------+-----------+
| UCLA Neiburger Award for excellence in teaching of the   | **1997**  |
| atmospheric sciences.                                    |           |
+----------------------------------------------------------+-----------+

SUMMARY OF BIBLIOGRAPHY

12 peer-reviewed (6 first-authored) journal articles.

34 (23 first-authored) conference presentations.

BIBLIOGRAPHY (Selection)

Russell, P.B., J. Redemann, et al., Comparison of aerosol single
scattering albedos derived by diverse techniques in two North Atlantic
experiments, *J. Atmos. Sci.,* *59*, 609-619, 2002.

Redemann, J., P.B. Russell, and P. Hamill, Dependence of aerosol light
absorption and single scattering albedo on ambient relative humidity for
sulfate aerosols with black carbon cores, *J. Geophys. Res.*, *106*,
27,485-27,495, 2001.

Redemann, J., et al., Retrieving the vertical structure of the effective
aerosol complex index of refraction from a combination of aerosol in
situ and remote sensing measurements during TARFOX, *J. Geophys. Res.* ,
*105*, 9949-9970, 2000.

Redemann, J., et al., Case studies of the vertical structure of the
direct shortwave aerosol radiative forcing during TARFOX, *J. Geophys.
Res., 105,* 9971-9979, 2000.

Redemann, J., R.P. Turco, R.F. Pueschel, M.A. Fenn, E.V. Browell and
W.B. Grant. A Multi-Instrument Approach for Characterizing the Vertical
Structure of Aerosol Properties: Case Studies in the Pacific Basin
Troposphere, *J. Geophys. Res., 103,* 23,287 - 23,298, 1998.

(a) Philip B. Russell

Abbreviated Curriculum Vitae

B.A., Physics, Wesleyan University (1965, Magna cum Laude; Highest
Honors). M.S. and Ph.D., Physics, Stanford University (1967 and 1971,
Atomic Energy Commission Fellow). M.S., Management, Stanford University
(1990, NASA Sloan Fellow).

Postdoctoral Appointee, National Center for Atmospheric Research
(1971-72, at University of Chicago and NCAR). Physicist to Senior
Physicist, Atmospheric Science Center, SRI International (1972-82).
Chief, Atmospheric Experiments Branch (1982-89), Acting Chief, Earth
System Science Division (1988-89), Chief, Atmospheric Chemistry and
Dynamics Branch (1989-95), Research Scientist (1995-present), NASA Ames
Research Center.

NASA Ames Honor Award (2002, for excellence in scientific research).
NASA Ames Associate Fellow (1995, for excellence in atmospheric
science). NASA Space Act Award (1989, for invention of Airborne
Autotracking Sunphotometer). NASA Exceptional Service Medal (1988, for
managing Stratosphere-Troposphere Exchange Project). Member, Phi Beta
Kappa and Sigma Xi.

Currently, Member, Science Teams for NASA's Earth Observing System
Inter-Disciplinary Science (EOS-IDS) and the Asian Pacific Regional
Aerosol Characterization Experiment (ACE-Asia) of the International
Global Atmospheric Chemistry (IGAC) Project.

Previously, Mission Scientist for ACE-Asia C-130 flights addressing
aerosol-radiation interactions. Co-coordinator for the CLEARCOLUMN
component of IGAC's Second Aerosol Characterization Experiment (ACE-2).
Coordinator for IGAC's Tropospheric Aerosol Radiative Forcing
Observational Experiment (TARFOX). Member, Science Teams for SAGE II and
SAGE III (satellite sensors of stratospheric aerosols, ozone, nitrogen
dioxide, and water vapor). Member, Science Team for Global Aerosol
Climatology Project (GACP).

Previously, Editor-in-Chief (1994-95) and Editor (1993, 1996),
*Geophysical Research Letters*. Chair, American Meteorological Society
Committee on Laser Atmospheric Studies (1979-82). Member, AMS Committee
on Radiation Energy (1979-81). Member, National Research Council
Committee on Army Basic Research (1979-81).

Previously, Project Scientist, Small High-Altitude Science Aircraft
(SHASA) Project to develop the Perseus A Remotely Piloted Aircraft (RPA,
1992-94). Member, NASA Red Team on Remote Sensing and Environmental
Monitoring of Planet Earth (1992-3). Leader, NASA Ames Earth Science
Advanced Aircraft (ESAA) Team (1990-94).

**SELECTED PUBLICATIONS (from 101 peer-reviewed papers)**

Russell, P. B., et al., Comparison of aerosol single scattering albedos
derived by diverse techniques in two North Atlantic experiments, *J.
Atmos. Sci.,* *59*, 609-619, 2002.

Russell, P. B., and J. Heintzenberg, An overview of the ACE-2 Clear Sky
Column Closure Experiment (CLEARCOLUMN), *Tellus B 52*, 463-483, 2000.

Bergstrom, R. W., and P. B. Russell, Estimation of aerosol radiative
effects over the mid-latitude North Atlantic region from satellite and
in situ measurements. *Geophys. Res. Lett., 26*, 1731-1734, 1999.

Russell, P. B., P. V. Hobbs, and L. L. Stowe, Aerosol properties and
radiative effects in the United States Mid-Atlantic haze plume: An
overview of the Tropospheric Aerosol Radiative Forcing Observational
Experiment (TARFOX), *J. Geophys. Res*., *104*, 2213-2222, 1999.

Russell, P. B., S. Kinne and R. Bergstrom, Aerosol climate effects:
Local radiative forcing and column closure experiments, *J. Geophys.
Res.,* *102*, 9397-9407, 1997.

Russell, P. B., et al. Global to microscale evolution of the Pinatubo
volcanic aerosol, derived from diverse measurements and analyses, *J.
Geophys. Res.*, *101*, 18,745-18,763, 1996.

Russell, P.B., et al. Post-Pinatubo optical depth spectra vs. latitude
and vortex structure: airborne tracking sunphotometer measurements in
AASE II, *Geophys. Res. Lett.*, *20*, 2571-2574, 1993.

Russell, P.B., L. Pfister, and H.B. Selkirk, \"The tropical experiment
of the Stratosphere-Troposphere Exchange Project (STEP): Science
objectives, operations, and summary findings, *J. Geophys. Res.*, *98*,
8563-8589, 1993.

Russell, P.B., and M.P. McCormick., SAGE II aerosol data validation and
initial data use: an introduction and overview, *J. Geophys. Res.*,
*94*, 8335-8338, 1989.

Russell, P.B., et al., Satellite and correlative measurements of the
stratospheric aerosol: III. Comparison of measurements by SAM II, SAGE,
dustsondes, filters, impactors, and lidar, *J. Atmos. Sci.*, *41*,
1791-1800, 1984.

(b) Brent N. Holben

Abbreviated Curriculum Vitae

+------------+----------------------------+---------------------------+
| *          | AERONET Project Leader     | Phone: 301 614-6658-2975  |
| *Present** |                            |                           |
|            | Code 923                   | FAX: 301 614-6695         |
| **         |                            |                           |
| Position** | Biospheric Sciences        | E-mail:                   |
|            |                            | [brent@ltpm               |
|            | NASA's Goddard Space       | ail.gsfc.nasa.gov](../bre |
|            | Flight Center              | nt@ltpmail.gsfc.nasa.gov) |
|            |                            |                           |
|            | Greenbelt, MD 20771 USA    |                           |
+------------+----------------------------+---------------------------+
| **         | Aerosol concentrations and |                           |
| Research** | properties measurements,   |                           |
|            | Global radiative forcing   |                           |
| **I        | and vegetation remote      |                           |
| nterests** | sensing in the SW and Mid  |                           |
|            | IR region.                 |                           |
+------------+----------------------------+---------------------------+
| **Summary  | Brent Holben has worked at |                           |
| of**       | NASA's GSFC for 24 years   |                           |
|            | performing research in     |                           |
| **Ex       | both ground-based and      |                           |
| perience** | satellite remote sensing   |                           |
|            | of vegetation and          |                           |
|            | aerosols. Additionally he  |                           |
|            | has developed innovative   |                           |
|            | methods for in orbit       |                           |
|            | calibration of satellite   |                           |
|            | visible and near-IR        |                           |
|            | sensors. He is the project |                           |
|            | leader for the AERONET     |                           |
|            | sun-sky radiometer network |                           |
|            | that is providing aerosol  |                           |
|            | spectral concentrations    |                           |
|            | and properties for the EOS |                           |
|            | algorithm validation       |                           |
|            | program as well as         |                           |
|            | validation for a variety   |                           |
|            | of other satellite systems |                           |
|            | and provides long term     |                           |
|            | aerosol characterization.  |                           |
|            | Holben has authored or co  |                           |
|            | authored over 120 peer     |                           |
|            | reviewed papers while at   |                           |
|            | Goddard.                   |                           |
+------------+----------------------------+---------------------------+

**Recent Selected Papers**

2002, Dubovik, O., **B.N.Holben**,T. Lapyonok, A.Sinyuk, M. I.
Mishchenko, P. Yang, and I.Slutsker: Non-spherical aerosol retrieval
method employing light scattering by spheriods,*Geophys. Res. Lett*.,
**29**, 54-1 - 54-4.

2001, **Holben, B.N**., D. Tanré, A. Smirnov, T.F. Eck, I. Slutsker, B
Chatenet, F. Lavenue,Y. Kaufman, J.V. Castle, A. Setzer, B.Markham, D.
Clark, R. Frouin, N A. Karneli. O\'Neill, C. Pietras, R. Pinker, K.
Voss, G. Zibordi, An emerging ground-based aerosol climatology: Aerosol
Optical Depth from AERONET, *J. Geophys. Res*, **106**, 12067-12097.

2000, Smirnov, A., **B.N.Holben**, T.F.Eck, O.Dubovik, I.Slutsker, Cloud
screening and quality control algorithms for the AERONET data base,
accepted to *Rem. Sens. Environ.,* **73**, 337-349.

2000, Dubovik**,** O., A.Smirnov, **B.N.Holben**, M.D.King, Y.J.
Kaufman, T.F.Eck, and I.Slutsker, "Accurasy assessments of aerosol
optical properties retrieved from AERONET Sun and sky-radiance
measurements", *J. Geophys. Res., **105*****,** 9791-9806.

1998, **Holben, B.N.**, T.F. Eck, I Slutsker, D. Tanré, J.P. Buis, A.
Setzer, E. Vermote, J.A. Reagan, Y.J. Kaufman, T. Nakajima, F. Lavenu,
I. Jankowiak, A. Smirnov, 1998. AERONET-A Federated Instrument Network
and Data Archive for Aerosol Characterization, *Rem. Sens. Environ*,
**66,**1-16.

(c) Oleg Dubovik

Abbreviated Curriculum Vitae

*Research Interest**: Inversion Developments in Remote Sensing and
Optical Diagnostics***

***Key Subjects:** Algorithm Development for Remote Sensing and Optical
Diagnostic, Light Scattering, Atmospheric Radiative Transfer, Numerical
Inversion, Estimation Theory, Statistics, Matrix Analysis.*

**[Education/Degree/]{.underline}**

1992 **Ph.D.** (Physics/Optics), Institute of Physics, Minsk, Belarus

1987-1989: Doctor Courses in Institute of Physics, Minsk, Belarus

1980-1985: Byelorussian State University, Minsk, Belarus

**M.S.** (Physics/Optics)

1978-1980: High School (with A-level in mathematics), Murmansk, Russia

**[Professional Career:]{.underline}**

2001-- Associate Research Scientist, Goddard Earth Sciences & Technology
Center, University of Maryland Baltimore County

1997--2001 Research Scientist, Science Systems and Applications Inc.,
under contract to NASA/Goddard Space Flight Center

1995--1997 Visiting Research Scientist, National Institute for
Environmental Studies, Tsukuba, Japan

1985-1995 Research Scientist, Institute of Physics, Minsk, Belarus

**[Selected Journal publications (of more than 50):]{.underline}**

Kaufman, Y. J., O. Dubovik, A. Smirnov and B. N. Holben, Remote sensing
of non-aerosol (anomalous) absorption in cloud free atmosphere, *J.
Geophys. Res. Lett.*, 10.1029/2001GL014399, 2002.

Dubovik, O., B. N. Holben, T. Lapyonok, A. Sinyuk, M. I. Mishchenko, P.
Yang and I. Slutsker, Non-spherical aerosol retrieval method employing
light scattering by spheroids, *Geophys. Res. Lett.*,
10.1029/2001GL014506,24 May 2002.

Takemura T., T. Nakajima, O. Dubovik, B. N. Holben and S. Kinne,
\"Single scattering albedo and radiative forcing of various aerosol
species with a global three-dimensional model\", *J. Climate*, 15, 333
-352, 2002.

Dubovik, O., B. N. Holben, T. F. Eck, A. Smirnov, Y. J. Kaufman, M. D.
King, D. Tanré, and I. Slutsker, "Variability of absorption and optical
properties of key aerosol types observed in worldwide locations", *J.
Atmos. Sci.*, *59*, 590-608, 2002.

Smirnov, A., B. N. Holben, Y. J. Kaufman, O. Dubovik, T. F. Eck, I.
Slutsker, C. Pietras, and R. N. Halthore, "Optical properties of
atmospheric aerosol in maritime environments", *J. Atm. Sci.*, *59*,
501-524, 2002.

Eck T. F., B. N. Holben, O. Dubovik, A. Smirnov, I. Slutsker, J. M.
Lobert and V. Ramanathan, M. Mukelabai, N. C. Hsu, N. T. O'Neill, and I.
Slutsker, "Column integrated aerosol optical properties over Maldives
during NE Monsoon for 1998-2000", *J. Geophys. Res.*, *106*,
28,555-28,566, 2001.

Pinker, R. T., G. Pandithurai, B. N. Holben, O. Dubovik, and T. O. Aro,
"A dust outbreak episode in sub-Sahel West Africa", *J. Geophys. Res.*,
*106*, 22,923 -22930, 2001.

Ferrare, R. A., D. D. Turner, L. A. Heilman, W. F. Feltz, O. Dubovik,
and T. P. Tooman, "Raman lidar measurements of aerosol
extinction-to-backscatter ration over Southern Great Plains", *J.
Geophys. Res.*, *106*, 20,333 -- 20,348, 2001.

Kaufman, Y. J., A. Smirnov, B. N. Holben, O. Dubovik, "Baseline maritime
aerosol: methodology to derive the optical thickness and scattering
properties", *Geophys. Res. Lett.*, *28*, 3251-3254, 2001.

O'Neill, N., O. Dubovik and T. F. Eck,, "A modified Angstrom coefficient
for characterization sub-micron aerosols", *Appl. Opt. , 40,* 2368-2375,
2001.

Kaufman, J. Y., D. Tanré, O. Dubovik, A. Karnieli, and L. A. Remer,
"Absorption of sunlight by dust as inferred from satellite and
ground-based remote sensing", *Geophys. Res. Lett.,* *28* , 1479-1483,
2001.

Eck T. F., B. N. Holben, D. E. Ward, O. Dubovik, J. S. Reid, A. Smirnov,
M. M. Mukelabai, N. C. Hsu, N. T. O'Neill, and I. Slutsker,
"Characterization of biomass burning aerosols in Zambia during the 1997
ZIBBEE field campaign", *J. Geophys. Res.*, *106* , 3425-3448, 2001.

Dubovik, O. and M. D. King, "A flexible inversion algorithm for
retrieval of aerosol optical properties from Sun and sky radiance
measurements", *J. Geophys. Res.,* *105*, 20,673-20,696, 2000.

Dubovik, O., A. Smirnov, B. N. Holben, M. D. King, Y. J. Kaufman, T. F.
Eck, and I. Slutsker, "Accuracy assessments of aerosol optical
properties retrieved from AERONET Sun and sky-radiance measurements",
*J. Geophys. Res.,105*, 9791-9806, 2000.

Dubovik, O., B. N. Holben, Y. J. Kaufman, M. Yamasoe, A. Smirnov, D.
Tanré, I. Slutsker, "Single-scattering albedo of smoke retrieved from
the sky radiance and solar transmittance measured from ground", *J.
Geophys. Res.,* *103*, 31903- 31924, 1998.

Dubovik, O. V, T. V. Lapyonok and S. L. Oshchepkov, "Improved technique
for data inversion: optical sizing of multicomponent aerosols", *Appl.
Opt*., *34*, 8422-8436,1995.

Dubovik, O. V, S. L. Oshchepkov, T. V. Lapyonok
"Iteration-regularization method of solution of nonlinear inverse
problems and its application to interpretation of the spectra of
brightness coefficient of a layer of water", Izv. Acad. Sci. USSR Atmos,
Oceanic Phys., 30, 103-110, 1994.

(d) James A. Eilers

Abbreviated Curriculum Vitae

**Education**

  ------ ------ ----------------------------------------------------------
  B.S.   1973   Engineering, University of California at Los Angeles, Los
                Angeles, CA

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

**Professional Experience**

[NASA Ames Research Center]{.underline} (1985-present)

\- AATS-14 Project Manager / Instrument Engineer (1998-present)

\- Project Manager - SONEX Airborne Field Campaign (1997-1998)

\- Research Engineer / Project Manager (1985-1997)

[Northrop Services Inc. - NASA Ames Research Center]{.underline}
(1979-1985)

\- Engineer - Kuiper Airborne Observatory

[University of California, Los Angeles]{.underline} (1979-1979)

\- Engineering Research Assistant

**Contributions**

Over 25 years of involvement in mechanical and system design of
scientific research equipment and instrumentation. In the past 15 years
have focused on atmospheric research instrumentation and projects,
primarily for airborne field studies. This includes contributing to
instrument proposals, instrument mechanical design, design project
management, and operation of instrumentation in the field. Have
significant experience with international field deployments as a member
of an instrument team, as well as at the project level as instrument
coordinator, and project manager.

**Specific Contributions**

\- Project manager and lead engineer for AATS-14 Sunphotometer Rework
Project

\- Project manager for the SONEX airborne field campaign.

\- Lead mechanical engineer and project manager for the Argus Airborne
Spectrometer

\- Lead engineer for OPTIMA open path spectrometer DDF project which
lead to proposals for the OPTIMA instrument for both the ER-2 and DC-8.

\- Project manager and lead engineer for Airborne Tunable Laser
Absorption Spectrometer (ATLAS).

**Professional Registration**

\- Professional Engineer in Mechanical Engineering (PE), State of
California

# CURRENT AND PENDING SUPPORT , PI's (B. Schmid and J. Redemann)

##  {#section-1 .unnumbered}

+--------------------------+-----------------------+------------------+
| **Short Title**          | **Agency/Task No.**   | **Duration**     |
+--------------------------+-----------------------+------------------+
| Vertically resolved      | DOE ARM Science Team  | 11/2002-10/2005  |
| aerosol optical          |                       |                  |
| properties over the ARM  | DE-AI03-03ER63535     |                  |
| SGP site                 |                       |                  |
+--------------------------+-----------------------+------------------+
| AATS-14 aboard the       | DOE ARM IOP funds     | 2/2003-12/2003   |
| CIRPAS Twin Otter during |                       |                  |
| the May 2003 Aerosol IOP | ITF 355506-A          |                  |
| over the SGP ARM site    |                       |                  |
+--------------------------+-----------------------+------------------+
| New Investigator         | NASA NAG5-12573       | 10/2002-9/2005   |
| Program:                 |                       |                  |
|                          |                       |                  |
| "Validating EOS Terra    |                       |                  |
| Sensor Data..."          |                       |                  |
+--------------------------+-----------------------+------------------+
| Global Aerosol           | NASA RTOP             | 10/1998-3/2003   |
| Climatology (GACP)       |                       |                  |
|                          | 622-44-75-10          |                  |
+--------------------------+-----------------------+------------------+
| ACE-2 & ACE-Asia Aerosol | NOAA Interagency      | 5/2000-4/2003    |
| Radiative Effect Studies | Transfer of Funds     |                  |
|                          | NA02AANRG0129         |                  |
+--------------------------+-----------------------+------------------+
| Satellite-Sunphotometer  | NASA RTOP             | 2/2000-12/2002   |
| Studies of Aerosol,...   |                       |                  |
|                          | 291-01-91-45          |                  |
+--------------------------+-----------------------+------------------+
| SOLVE-2 Science Team     | NASA                  | 8/2002-6/2003    |
+--------------------------+-----------------------+------------------+

# APPENDIX A: Ames Airborne Tracking Sunphotometer, AATS-14

Philip B. Russell, John M. Livingston, Beat Schmid, Jens Redemann, and
James Eilers

NASA Ames Research Center, Moffett Field, CA 94035-1000

prussell@mail.arc.nasa.gov

The NASA Ames Airborne Tracking Sunphotometers measure the transmission
of the solar beam in a number of spectral channels. AATS-14, shown in
Fig. 1, has 14 such channels. Azimuth and elevation motors controlled by
differential sun sensors rotate a tracking head so as to lock on to the
solar beam and keep detectors normal to it. The tracking head of the
instrument mounts external to the aircraft skin, to minimize blockage by
aircraft structures and also to avoid data contamination by
aircraft-window effects.

![](media/image15.wmf)Each channel consists of a baffled entrance path,
interference filter, photodiode detector, and preamplifier. Channel
filters are at wavelengths from 354 to 2139 nm (Fig. 2), chosen to allow
separation of aerosol, water vapor, and ozone transmission. The
filter/detector sets are temperature-controlled to avoid
thermally-induced calibration changes. Detectors in the two
longest-wavelength channels incorporate thermoelectric coolers. The
other 12 channels are maintained at an elevated temperature by foil
heaters.

Sun tracking is achieved continuously, independent of aircraft pitch,
roll, and yaw, provided rates do not exceed \~8° s^-1^ and the sun is
above aircraft horizon and unblocked by clouds or aircraft obstructions
(e.g., tail, antennas). AATS-14 uses a quad-cell photodiode to derive
azimuth and elevation tracking-error signals.

Data are digitized and recorded by an onboard data acquisition and
control system. Realtime data processing and color display are routinely
provided. The realtime science data set includes the detector signals,
derived optical depths and water vapor column content, detector
temperature, sun tracker azimuth and elevation angles, tracking errors,
and time. Radiometric calibration is determined via Langley plots,
either at high-mountain observatories or on specially designed flights.
Repeated calibrations show that the instrument maintains its calibration
(including window and filter transmittance, detector responsivity and
electronic gain) to within 1% in most spectral channels for periods of
several months to a year.

AATS-14 was developed under the NASA Environmental Research Aircraft and
Sensor Technology (ERAST) Program. AATS-14 is designed to operate on a
variety of aircraft, some of which may be remotely piloted or
autonomous. Hence it can locate and track the sun without input from an
operator and record data in a self contained data system. In addition,
it can interface to an aircraft-provided telemetry system, so as to
receive and execute commands from a remote operator station, and
transmit science and instrument-status data to that station.

AATS-14 made its first science flights on the Pelican (modified Cessna)
aircraft of the Center for Interdisciplinary Remotely Piloted Aircraft
Studies (CIRPAS) during the Tropospheric Aerosol Radiative Forcing
Observational Experiment (TARFOX) in July 1996 \[Russell et al., 1999\].
Other missions in which AATS-14 has participated include the second
Aerosol Characterization Experiment (ACE-2) \[Schmid et al., 2000\],
South African Regional Science Initiative (SAFARI) 2000 \[Schmid et al.,
2002\], Asian Pacific Regional Aerosol Characterization Experiment
(ACE-Asia) \[Russell et al., 2002\], and Chesapeake Lighthouse and
Aircraft Measurements for Satellites (CLAMS) \[Redemann et al., 2002\].

**Figure 1.** Fourteen-channel Ames Airborne Tracking Sunphotometer
(AATS-14). Dimensions are in inches

![](media/image16.wmf){width="4.776388888888889in"
height="4.093055555555556in"}

**Figure 2.** AATS-14 channel wavelengths (vertical lines with arrows)
in relation to atmospheric spectra. The spectra of transmittance T of
the direct solar beam at sea level were calculated using MODTRAN-4.3
with a Midlatitude Summer atmosphere, a rural spring-summer tropospheric
aerosol model (Vis = 23 km), and the sun at the zenith. Current center
wavelengths of channel filters are 354, 380, 453, 499, 519, 604, 675,
778, 865, 941, 1019, 1241, 1558, 2139 nm. Filter full widths at
half-maximum (FWHM) are 5 nm, except for the 353 and 2139 nm channels,
which have FWHM 2 and 17 nm, respectively.

**References**

Russell, P. B., J. M. Livingston, P. Hignett, S. Kinne, J. Wong, and P.
V. Hobbs, Aerosol-induced radiative flux changes off the United States
Mid-Atlantic coast: Comparison of values calculated from sunphotometer
and in situ data with those measured by airborne pyranometer, *J.
Geophys. Res.,* *104*, 2289-2307, 1999.

Schmid, B., Livingston, J. M., Russell, P. B., Durkee, P. A., Collins,
D. R., Flagan, R. C., Seinfeld, J. H., Gassó, S., Hegg, D. A., Öström,
E., Noone, K. J., Welton, E. J., Voss, K., Gordon, H. R., Formenti, P.,
and Andreae, M. O., Clear sky closure studies of lower tropospheric
aerosol and water vapor during ACE-2 using airborne sunphotometer,
airborne in-situ, space-borne, and ground-based measurements. *Tellus B
52,* 568-593, 2000.

Redemann, J., B. Schmid, J. M. Livingston, P. B. Russell, J. A. Eilers,
P. V. Hobbs, R. Kahn, W. L. Smith, Jr., B. N. Holben, C. K. Rutledge, M.
C. Pitts, M. I. Mishchenko, B. Cairns, J. V. Martins, and T. P.
Charlock, Airborne Measurements of Aerosol Optical Depth and Columnar
Water Vapor in Support of the Chesapeake Lighthouse and Aircraft
Measurements for Satellites (CLAMS) Experiment, 2001, Abstracts, 11^th^
Conference on Atmospheric Radiation, American Meteorological Society,
Ogden, UT, June 3-7, pp. 20, 2002.

P. B. Russell, P. J. Flatau, F. P. J. Valero, T. Nakajima, B. Holben, P.
Pilewskie, M. Bergin, B. Schmid, R. W. Bergstrom, A. Vogelmann, B. Bush,
J. Redemann, S. Pope, J. Livingston, S. Leitner, N. C. Hsu, J. Wang, J.
Seinfeld, D. Hegg, P. Quinn, and D. Covert, Overview of ACE-Asia Spring
2001 investigations on aerosol-radiation interactions,11th Conference on
Atmospheric Radiation, American Meteorological Society, Ogden, Utah, 3-7
June 2002, Postprint Volume, pp. 1-4.

Schmid, B., J. Redemann, P. B. Russell, P. V. Hobbs, D. L. Hlavka, M. J.
McGill, B. N. Holben, E. J. Welton, J. Campbell, O. Torres, R. A. Kahn,
D. J. Diner, M. C. Helmlinger, D. A. Chu, C. Robles Gonzalez, and G. de
Leeuw, Coordinated airborne, spaceborne, and ground-based measurements
of massive, thick aerosol layers during the dry season in Southern
Africa, J. Geophys. Res., in press, 2002.

# APPENDIX B: Ames Airborne Sensor Facility Calibration Laboratory Capabilities

[Equipment]{.underline} [Purpose]{.underline}

Interferometer (Bomem MB 100) Spectral Calibration in range from 2.5 to
25 micrometers.

ACTON Monochromator with gratings Spectral Calibration in range

in range from 0.4 to 15 micrometers from 0.4 to 15 micrometers.

illuminated by Oriel light sources

Two 30" Integrating Spheres and two Radiometric calibration in

20" Integrating Hemispheres range from 0.4 to 2.5 micrometers

ASD portable spectroradiometer Transfer of Spectral Radiance (range from
0.4 to 2.5 micrometers) from Standard Lamp to Integrating Sphere.
Reflectance and Transmission measurements. Field calibrations.

Cary 14 Spectrophotometer Filter Transmission

> (range from 0.4 to 2.5 micrometers) measurements and future Sphere
> Calibration

Extended Black Body Source Radiometric calibration in range from 3 to 25
micrometers

NIST FEL Standard lamp with Primary Standard for Sphere Labsphere
Spectrolon panel calibration

Optical Bench w/ 12" dia. Interfaces to spectral sources

collimator

Focus Bench w/ 8" dia. Focusing of optical systems

collimator & bar targets

Thermal Chamber w/ Radiometric and Spectral

view port calibration at simulated flight temperatures.